Enantiomers of spiro-oxindole compounds and their uses as therapeutic agents

ABSTRACT

This invention is directed to the (S)-enantiomer of the compound of formula (I): 
     
       
         
         
             
             
         
       
     
     or a pharmaceutically acceptable solvate or prodrug thereof. This (S)-enantiomer is useful for the treatment of diseases or conditions, such as pain, which are ameliorated or alleviated by the modulation of voltage-gated sodium channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/825,168, filed Jun. 28, 2010, now pending, which claims thebenefit under 37 U.S.C. §119(e) of U.S. Provisional Patent ApplicationNo. 61/221,424, filed Jun. 29, 2009. These applications are incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

This invention is directed to a specific enantiomer of a spiro-oxindolecompound, specifically to the enantiomer's use in human or veterinarytherapeutics for treating diseases or conditions in a mammal, preferablya human, which are ameliorated or alleviated by the modulation,preferably inhibition, of voltage-gated sodium channels.

BACKGROUND OF THE INVENTION

PCT Published Patent Application No. WO 2006/110917, the disclosure ofwhich is incorporated in full by reference herein, discloses certainspiro-oxindole compounds, in particular,1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one,i.e., the compound of the following formula (I):

These compounds are disclosed therein as being useful in treatingdiseases or conditions, such as pain, in mammals, preferably humans,which are ameliorated or alleviated by the modulation, preferablyinhibition, of voltage-gated sodium channels.

SUMMARY OF THE INVENTION

The present invention is directed to the discovery that the(S)-enantiomer and the (R)-enantiomer of the following compound offormula (I):

demonstrate a difference in potency for the inhibition of voltage-gatedsodium channel activity.

Accordingly, in one aspect, the invention provides the (S)-enantiomer of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one,i.e., the (S)-enantiomer having the following formula (I-S):

or a pharmaceutically acceptable solvate or prodrug thereof. Preferably,the (S)-enantiomer is substantially free of the (R)-enantiomer.

In another aspect, the invention provides a pharmaceutical compositioncomprising the (S)-enantiomer, or a pharmaceutically acceptable solvateor prodrug thereof, as set forth above, preferably substantially free ofthe (R)-enantiomer, and one or more pharmaceutically acceptableexcipients.

In one embodiment, the present invention relates to a pharmaceuticalcomposition comprising the (S)-enantiomer, or a pharmaceuticallyacceptable solvate or prodrug thereof, as set forth above, preferablysubstantially free of the (R)-enantiomer, in a pharmaceuticallyacceptable carrier and in an amount effective to treat diseases orconditions related to pain when administered to an animal, preferably amammal, most preferably a human.

In another aspect, the invention provides pharmaceutical therapy incombination with the (S)-enantiomer, or a pharmaceutically acceptablesolvate or prodrug thereof, as set forth above, preferably substantiallyfree of the (R)-enantiomer, and one or more other existing therapies oras any combination thereof to increase the efficacy of an existing orfuture drug therapy or to decrease the adverse events associated withthe existing or future drug therapy. In one embodiment, the presentinvention relates to a pharmaceutical composition combining the(S)-enantiomer, or a pharmaceutically acceptable solvate or prodrugthereof, as set forth above, preferably substantially free of the(R)-enantiomer, with established or future therapies for the indicationslisted in the invention.

In another aspect, the invention provides a method of treating a diseaseor a condition in a mammal, preferably a human, wherein the disease orcondition is selected from the group consisting of pain, depression,cardiovascular diseases, respiratory diseases, psychiatric diseases,neurological diseases and seizures, and combinations thereof, whereinthe method comprises administering to the mammal in need thereof atherapeutically effective amount of the (S)-enantiomer, as set forthabove, or a pharmaceutically acceptable solvate or prodrug thereof.

In another aspect, the invention provides a method for the treatment ofpain in a mammal, preferably a human, wherein the method comprisesadministering to the mammal in need thereof a therapeutically effectiveamount of the (S)-enantiomer, or a pharmaceutically acceptable solvateor prodrug thereof, as set forth above, preferably substantially free ofthe (R)-enantiomer.

In another aspect, the present invention provides a method for treatingor lessening the severity of a disease, condition, or disorder whereactivation or hyperactivity of one or more voltage-gated sodium channelproteins, including, but not limited to, Na_(V)1.1, Na_(V)1.2,Na_(V)1.3, Na_(V)1.4, Na_(V)1.5, Na_(V)1.6, Na_(V)1.7, Na_(V)1.8, orNa_(V)1.9 voltage-gated sodium channel, is implicated in the disease,condition or disorder, wherein the method comprises administering to themammal in need thereof a therapeutically effective amount of the(S)-enantiomer, or a pharmaceutically acceptable solvate or prodrugthereof, as set forth above, preferably substantially free of the(R)-enantiomer.

In another aspect, the invention provides a method of treating diseasesor conditions in mammals, preferably humans, which are associated withthe activity of voltage-gated sodium channels. Accordingly, theinvention provides a method of treating diseases or conditions inmammals, preferably humans, which are ameliorated or alleviated by themodulation, preferably inhibition, of voltage-gated sodium channels.Examples of such diseases or conditions include, but are not limited to,pain of any nature and origin, pain associated with HIV, HIV treatmentinduced neuropathy, trigeminal neuralgia, post-herpetic neuralgia,diabetic neuropathy, complex regional pain syndrome (CRPS), ParoxysmalExtreme Pain Disorder (PEPD), eudynia, heat sensitivity, sarcoidosis,irritable bowel syndrome, Crohns disease, pain associated with multiplesclerosis (MS), motor impairment associated with MS, amyotrophic lateralsclerosis (ALS), pruritis, hypercholesterolemia, benign prostatichyperplasia, peripheral neuropathy, arthritis, rheumatoid arthritis,osteoarthritis, paroxysmal dystonia, periodic paralysis, myastheniasyndromes, myotonia, malignant hyperthermia, cystic fibrosis,pseudoaldosteronism, rhabdomyolysis, bipolar depression, anxiety,schizophrenia, illness due to exposure to insecticides or other agentsthat promote neuronal or muscle hyperexcitability, familialerythermalgia, secondary erythermalgia, familial rectal pain, familialfacial pain, migraine, headache, neuralgiform headache, familialhemiplegic migraine, conditions associated with cephalic pain, sinusheadache, tension headache, phantom limb pain, peripheral nerve injury,cancer, epilepsy, partial and general tonic seizures, restless legsyndrome, arrhythmias, fibromyalgia, neuroprotection under ischaemicconditions caused by stroke, glaucoma or neural trauma,tachy-arrhythmias, atrial fibrillation and ventricular fibrillation,wherein the method comprises administering to the mammal in need thereofa therapeutically effective amount of the (S)-enantiomer, or apharmaceutically acceptable solvate or prodrug thereof, as set forthabove, preferably substantially free of the (R)-enantiomer.

In another aspect, the invention provides a method of treating a diseaseor condition in a mammal, preferably a human, by the inhibition of ionflux through a voltage-gated sodium channel in the mammal, wherein themethod comprises administering to the mammal in need thereof atherapeutically effective amount of the (S)-enantiomer, or apharmaceutically acceptable solvate or prodrug thereof, as set forthabove, preferably substantially free of the (R)-enantiomer.

In another aspect, the invention provides a method of decreasing ionflux through a voltage-gated sodium channel in a cell in a mammal,wherein the method comprises contacting the cell with the(S)-enantiomer, or a pharmaceutically acceptable solvate or prodrugthereof, as set forth above, preferably substantially free of the(R)-enantiomer.

The invention further provides the use of the (S)-enantiomer, or apharmaceutically acceptable solvate or prodrug thereof, as set forthabove, preferably substantially free of the (R)-enantiomer, in thepreparation of a medicament composition in the treatment of a disease orcondition that is associated with the activity of a voltage-gated sodiumchannel. Accordingly, the invention provides the use of the(S)-enantiomer, or a pharmaceutically acceptable solvate or prodrugthereof, as set forth above, preferably substantially free of the(R)-enantiomer, in the preparation of a medicament composition in thetreatment of a disease or condition which is ameliorated or alleviatedby the modulation, preferably inhibition, of a voltage-gated sodiumchannel.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1 shows concentration-response relationship for the (S)- and(R)-enantiomers in the Guanidine Influx Assay from Biological Example 1herein.

FIG. 2 shows comparison of the efficacy of the (S)- and (R)-enantiomerswith oral dosing in an inflammatory pain model from Biological Example 3herein.

FIG. 3 shows comparison of the efficacy of the (S)- and (R)-enantiomerswith topical administration in a neuropathic pain model from BiologicalExample 3 herein.

FIG. 4 shows the time course of histamine-induced itching in untreatedmice in the in vivo assay described in Biological Example 7. Data areexpressed as Mean±SD itching bouts.

FIG. 5 shows the efficacy against histamine-induced itch of a topicallyapplied ointment containing 8% (w/v) of the (S)-enantiomer. Data areexpressed as Mean±SD itching bouts.

FIG. 6 shows the efficacy of the (S)-enantiomer againsthistamine-induced itch when administered orally rather than topically.Data are expressed as Mean±SD itching bouts.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used in the specification and appended claims, unless specified tothe contrary, the following terms have the meaning indicated:

“Analgesia” refers to an absence of pain in response to a stimulus thatwould normally be painful.

“Allodynia” refers to a condition in which a normally innocuoussensation, such as pressure or light touch, is perceived as beingpainful.

“Enantiomers” refers to asymmetric molecules that can exist in twodifferent isomeric forms which have different configurations in space.Other terms used to designate or refer to enantiomers include“stereoisomers” (because of the different arrangement or stereochemistryaround the chiral center; although all enantiomers are stereoisomers,not all stereoisomers are enantiomers) or “optical isomers” (because ofthe optical activity of pure enantiomers, which is the ability ofdifferent pure enantiomers to rotate plane-polarized light in differentdirections). Because they do not have a plane of symmetry, enantiomersare not identical with their mirror images; molecules which exist in twoenantiomeric forms are chiral, which means that they can be regarded asoccurring in “left” and “right” handed forms. The most common cause ofchirality in organic molecules is the presence of a tetrahedral carbonbonded to four different substituents or groups. Such a carbon isreferred to as a chiral center, or stereogenic center. A method forindicating the three-dimensional arrangement of atoms (or theconfiguration) at a stereogenic center is to refer to the arrangement ofthe priority of the groups when the lowest priority group is orientedaway from a hypothetical observer: If the arrangement of the remainingthree groups from the higher to the lower priority is clockwise, thestereogenic center has an “R” (or “D”) configuration; if the arrangementis counterclockwise, the stereogenic center has an “S” (or “L”)configuration.

Enantiomers have the same empirical chemical formula, and are generallychemically identical in their reactions, their physical properties, andtheir spectroscopic properties. However, enantiomers show differentchemical reactivity toward other asymmetric compounds, and responddifferently toward asymmetric physical disturbances. The most commonasymmetric disturbance is polarized light.

An enantiomer can rotate plane-polarized light; thus, an enantiomer isoptically active. Two different enantiomers of the same compound willrotate plane-polarized light in the opposite direction; thus, the lightcan be rotated to the left or counterclockwise for a hypotheticalobserver (this is levarotatory or “l”, or minus or “−”) or it can berotated to the right or clockwise (this is dextrorotatory or “d” or plusor “+”). The sign of optical rotation (+) or (−), is not related to theR,S designation. A mixture of equal amounts of two chiral enantiomers iscalled a racemic mixture, or racemate, and is denoted either by thesymbol (+/−) or by the prefix “d,l” to indicate a mixture ofdextrorotatory and levorotatory forms. The compound of formula (I), asdescribed herein, is a racemate. Racemates or racemic mixtures show zerooptical rotation because equal amounts of the (+) and (−) forms arepresent. In general, the presence of a single enantiomer rotatespolarized light in only one direction; thus, a single enantiomer isreferred to as optically pure.

The designations “R” and “S” are used to denote the absoluteconfiguration of the molecule about its chiral center(s). Thedesignations may appear as a prefix or as a suffix; they may or may notbe separated from the enantiomer name by a hyphen; they may or may notbe hyphenated; and they may or may not be surrounded by parentheses.

The designations or prefixes “(+) and (−)” are employed herein todesignate the sign of rotation of plane-polarized light by the compound,with (−) meaning that the compound is levorotatory (rotates to theleft). A compound prefixed with (+) is dextrorotatory (rotates to theright).

“Resolution” or “resolving” when used in reference to a racemic compoundor mixture refers to the separation of a racemate into its twoenantiomeric forms (i.e., (+) and (−); (R) and (S) forms).

“Enantiomeric excess” or “ee” refers to a product wherein one enantiomeris present in excess of the other, and is defined as the absolutedifference in the mole fraction of each enantiomer. Enantiomeric excessis typically expressed as a percentage of an enantiomer present in amixture relative to the other enantiomer. For purposes of thisinvention, the (S)-enantiomer of the invention is considered to be“substantially free” of the (R)-enantiomer when the (S)-enantiomer ispresent in enantiomeric excess of greater than 80%, preferably greaterthan 90%, more preferably greater than 95% and most preferably greaterthan 99%.

The chemical naming protocol and structure diagrams used herein are amodified form of the I.U.P.A.C. nomenclature system, using the ACD/NameVersion 9.07 software program. For example, the compound of formula (I),as set forth above in the Summary of the Invention, is named herein as1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one.The corresponding (S)-enantiomer, i.e., the (S)-enantiomer of formula(I-S), as set forth above in the Summary of the Invention, is namedherein as(S)-1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one.The corresponding (R)-enantiomer, the (R)-enantiomer of the followingformula (I-R):

or a pharmaceutically acceptable solvate or prodrug thereof, is namedherein as(R)-1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one.

“Prodrugs” is meant to indicate a compound that may be converted underphysiological conditions or by solvolysis to a biologically activecompound of the invention. Thus, the term “prodrug” refers to ametabolic precursor of a compound of the invention that ispharmaceutically acceptable. A prodrug may be inactive when administeredto a subject in need thereof, but is converted in vivo to an activecompound of the invention. Prodrugs are typically rapidly transformed invivo to yield the parent compound of the invention, for example, byhydrolysis in blood. The prodrug compound often offers advantages ofsolubility, tissue compatibility or delayed release in a mammalianorganism (see, Bundgard, H., Design of Prodrugs (1985), pp. 7-9, 21-24(Elsevier, Amsterdam)). A discussion of prodrugs is provided in Higuchi,T., et al., “Pro-drugs as Novel Delivery Systems,” A.C.S. SymposiumSeries, Vol. 14, and in Bioreversible Carriers in Drug Design, Ed.Edward B. Roche, American Pharmaceutical Association and Pergamon Press,1987, both of which are incorporated in full by reference herein.

The term “prodrug” is also meant to include any covalently bondedcarriers, which release the active compound of the invention in vivowhen such prodrug is administered to a mammalian subject. Prodrugs of acompound of the invention may be prepared by modifying functional groupspresent in the compound of the invention in such a way that themodifications are cleaved, either in routine manipulation or in vivo, tothe parent compound of the invention. Prodrugs include compounds of theinvention wherein a hydroxy, amino or mercapto group is bonded to anygroup that, when the prodrug of the compound of the invention isadministered to a mammalian subject, cleaves to form a free hydroxy,free amino or free mercapto group, respectively. Examples of prodrugsinclude, but are not limited to, acetate, formate and benzoatederivatives of alcohol or amide derivatives of amine functional groupsin the compounds of the invention and the like.

The invention disclosed herein is also meant to encompass the(S)-enantiomer and the (R)-enantiomer disclosed herein beingisotopically-labelled by having one or more atoms replaced by an atomhaving a different atomic mass or mass number. Examples of isotopes thatcan be incorporated into the disclosed compounds include isotopes ofhydrogen, carbon, nitrogen, oxygen, such as ²H, ³H, ¹¹C, ¹³C, ¹⁴C, ¹³N,¹⁵N, ¹⁵O, ¹⁷O, ¹⁸O, and ¹⁸F, respectively. These radiolabelled compoundscould be useful to help determine or measure the effectiveness of thecompounds, by characterizing, for example, the site or mode of action onthe voltage-gated sodium channels, or binding affinity topharmacologically important site of action on the voltage-gated sodiumchannels. Isotopically-labelled compounds are useful in drug and/orsubstrate tissue distribution studies. The radioactive isotopes tritium,i.e. ³H, and carbon-14, i.e. ¹⁴C, are particularly useful for thispurpose in view of their ease of incorporation and ready means ofdetection. A radioligand incorporating tritium (³H) is particularlyuseful for ligand binding studies with membranes that containvoltage-gated sodium channels because tritium has a long half-life ofdecay and the emission is of relatively low energy and the radioisotopeis therefore relatively safe. The radioligand is typically prepared byexchange of tritium with a hydrogen in an unlabeled compound. Theidentification of active and inactive enantiomers of a particularracemate facilitates the development of a ligand binding assay becausethe unlabeled inactive enantiomer can be added to the assay to reduce,eliminate or otherwise control non-specific binding of the tritiatedactive enantiomer.

Substitution with heavier isotopes such as deuterium, i.e. ²H, mayafford certain therapeutic advantages resulting from greater metabolicstability, for example, increased in vivo half-life or reduced dosagerequirements, and hence may be preferred in some circumstances.

Substitution with positron emitting isotopes, such as ¹¹C, ¹⁸F, ¹⁵O and¹³N, can be useful in Positron Emission Topography (PET) studies forexamining substrate receptor occupancy. Isotopically-labeled enantiomersof the invention can generally be prepared by conventional techniquesknown to those skilled in the art or by processes analogous to thosedescribed herein using an appropriate isotopically-labeled reagent inplace of the non-labeled reagent previously employed.

The invention disclosed herein is also meant to encompass the in vivometabolic products of the disclosed enantiomers. Such products mayresult from, for example, the oxidation, reduction, hydrolysis,amidation, esterification, and the like of the administered compound,primarily due to enzymatic processes. Accordingly, the inventionincludes metabolic products produced by a process comprising contactingan enantiomer of this invention with a mammal for a period of timesufficient to yield the metabolic product. Such metabolic products maybe identified by administering a radiolabelled enantiomer of theinvention in a detectable dose to an animal, such as rat, mouse, guineapig, monkey, or to human, allowing sufficient time for metabolism tooccur, and isolating the metabolic product from the urine, blood orother biological samples.

“Selectivity” and “selective” as used herein is a relative measure ofthe tendency for a compound of the invention to preferentially associatewith one thing as opposed to another (or group of others), as between oramong voltage-gated sodium channels. For example, the selectivity may bedetermined by comparative measurements of the kinetics and equilibriumbinding affinity and/or functional measures of ion transport through thevoltage-gated sodium channels. The tendency of a compound to associatewith a voltage-gated sodium channel can be measured by many differenttechniques, and many types of association are known to those skilled inthe art, as disclosed elsewhere herein. Selectivity means that in aparticular type of association, measured in a specific way, a compounddemonstrates a tendency or preference to associate with onevoltage-gated sodium channel as opposed to one or more of the othervoltage-gated sodium channels. This association may be different fordifferent types of assays or different ways of measurement.

“Stable enantiomer” and “stable structure” are meant to indicate acompound that is sufficiently robust to survive isolation to a usefuldegree of purity from a reaction mixture, and formulation into anefficacious therapeutic agent.

“Mammal” includes humans and both domestic animals such as laboratoryanimals and household pets, (e.g. cats, dogs, swine, cattle, sheep,goats, horses, and rabbits), and non-domestic animals such as wildlifeand the like.

“Pharmaceutically acceptable carrier, diluent or excipient” includeswithout limitation any adjuvant, carrier, excipient, glidant, sweeteningagent, diluent, preservative, dye/colorant, flavor enhancer, surfactant,wetting agent, dispersing agent, suspending agent, stabilizer, isotonicagent, solvent, or emulsifier which has been approved by, fornon-limiting example, the United States Food and Drug Administration,Health Canada or the European Medicines Agency, as being acceptable foruse in humans or domestic animals.

A “pharmaceutical composition” refers to a formulation of a compound ofthe invention and a medium generally accepted in the art for thedelivery of the biologically active compound to mammals, e.g., humans.Such a medium includes all pharmaceutically acceptable carriers,diluents or excipients therefore.

The pharmaceutical compositions of the invention comprise one or morepharmaceutically acceptable excipients, which include, but are notlimited to, any solvent, adjuvant, bioavailability enhancer, carrier,glidant, sweetening agent, diluent, preservative, dye/colorant, flavorenhancer, surfactant, wetting agent, dispersing agent, suspending agent,stabilizer, isotonic agent, buffer and/or emulsifier approved by, fornon-limiting example, the United States Food and Drug Administration,Health Canada or the European Medicines Agency, as being acceptable foruse in humans or domestic animals. Exemplary pharmaceutically acceptableexcipients include, but are not limited to, the following:

-   -   benzyl alcohol    -   benzyl benzoate    -   caprylocaproyl macrogolglycerides (e.g. Labrasol®)    -   dimethylamine (“DMA”)    -   ethanol    -   2-(2-ethoxyethoxy)ethanol (e.g., Transcutol®)    -   glucose (solution)    -   glyceryl caprylate/caprate and PEG-8 (polyethylene glycol)        caprylate/caprate complex (e.g., Labrasol®)    -   isopropyl alcohol    -   Lauroyl Macrogol-32 Glycerides (e.g. Gelucire® 44/14)    -   macrogol-15 hydroxystearate (e.g., Solutol® HS15)    -   medium chain triglycerides (e.g., Miglyol® 810, Miglyol® 840 or        Miglyol® 812)    -   peanut oil    -   polysorbate 80 (e.g., Tween® 80)    -   polyethylene glycol (PEG)    -   polyethylene glycol 400 (PEG400, e.g., Lutrol® E 400)    -   polyethylene glycol 6000    -   polyoxyl 35 castor oil (e.g., Cremophor® EL)    -   polyoxyl 40 hydrogenated castor oil (e.g., Cremophor® RH 40)    -   propylene glycol (PG)    -   propylene glycol monocaprylate (Capryol® 90)    -   soybean oil    -   sulfobutylether-β-cyclodextrin (e.g., Capitsol®)    -   TPGS (α-tocopherol polyethylene glycol succinate)    -   water

Additional pharmaceutically acceptable excipients are disclosed herein.

Often crystallizations produce a solvate of the compound of theinvention. As used herein, the term “solvate” refers to an aggregatethat comprises one or more molecules of a compound of the invention withone or more molecules of solvent. The solvent may be water, in whichcase the solvate may be a hydrate. Alternatively, the solvent may be anorganic solvent. Thus, the compounds of the present invention may existas a hydrate, including a monohydrate, dihydrate, hemihydrate,sesquihydrate, trihydrate, tetrahydrate and the like, as well as thecorresponding solvated forms. The compound of the invention may be truesolvates, while in other cases, the compound of the invention may merelyretain adventitious water or be a mixture of water plus someadventitious solvent.

“Therapeutically effective amount” refers to that amount of a compoundof the invention which, when administered to a mammal, preferably ahuman, is sufficient to effect treatment, as defined below, of a diseaseor condition of interest in the mammal, preferably a human. The amountof a compound of the invention which constitutes a “therapeuticallyeffective amount” will vary depending on the compound, the condition andits severity, the manner of administration, and the age of the mammal tobe treated, but can be determined routinely by one of ordinary skill inthe art having regard to his own knowledge and to this disclosure.

“Treating” or “treatment” as used herein covers the treatment of thedisease or condition of interest in a mammal, preferably a human, havingthe disease or condition of interest, and includes:

(i) preventing the disease or condition from occurring in a mammal, inparticular, when such mammal is predisposed to the condition but has notyet been diagnosed as having it;

(ii) inhibiting the disease or condition, i.e., arresting itsdevelopment;

(iii) relieving the disease or condition, i.e., causing regression ofthe disease or condition; or

(iv) relieving the symptoms resulting from the disease or condition,i.e., relieving pain with or without addressing the underlying diseaseor condition.

As used herein, the terms “ameliorating”, “ameliorated”, “alleviating”or “alleviated” are to be given their generally acceptable definitions.For example, to “ameliorate” generally means to make better or toimprove a condition relative to the condition prior to the amelioratingevent. To “alleviate” generally means to make a condition more bearablerelative to the condition prior to the alleviating event. As usedherein, “ameliorating” or “ameliorated” can refer to a disease orcondition that is made better or improved by the administration of acompound of the invention. As used herein, “alleviating” or “alleviated”can refer to a disease or condition that is made bearable by theadministration of a compound of the invention. For example,“alleviating” pain would include reducing the severity or amount ofpain.

As used herein, the terms “disease”, “disorder” and “condition” may beused interchangeably or may be different in that the particular maladyor condition may not have a known causative agent (so that etiology hasnot yet been worked out) and it is therefore not yet recognized as adisease but only as an undesirable condition or syndrome, wherein a moreor less specific set of symptoms have been identified by clinicians.

Utility and Testing of the Compounds of the Invention

The present invention relates to the (S)-enantiomer of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one,pharmaceutical compositions and methods of using the (S)-enantiomer ofthe invention and pharmaceutical compositions for the treatment ofdiseases or conditions which are ameliorated or alleviated by themodulation, preferably inhibition, of voltage-gated sodium channels,preferably diseases and conditions related to pain and pruritis; centralnervous system conditions such as epilepsy, restless leg syndrome,anxiety, depression and bipolar disease; cardiovascular conditions suchas arrhythmias, atrial fibrillation and ventricular fibrillation;neuromuscular conditions such as muscle paralysis, myotonia or tetanus;neuroprotection against stroke, neural trauma and multiple sclerosis;and channelopathies such as erythromelalgia and familial rectal painsyndrome, by administering to a patient in need of such treatment aneffective amount of a voltage-gated sodium channel blocker modulating,especially inhibiting, agent, preferably the enantiomers of theinvention.

In general, the present invention provides a method for treating amammal, preferably a human, for, or protecting a mammal, preferably ahuman, from developing, a disease or condition that is associated withthe activity of voltage-gated sodium channels, especially pain, whereinthe method comprises administering to the mammal a therapeuticallyeffective amount of the (S)-enantiomer, or a pharmaceutically acceptablesolvate or prodrug thereof, as set forth above in the Summary of theInvention, wherein the (S)-enantiomer modulates, preferably inhibits,the activity of one or more of the voltage-gated sodium channels.

The voltage-gated sodium channel family of proteins has been extensivelystudied and shown to be involved in a number of vital body functions.Research in this area has identified variants of the alpha subunits thatresult in major changes in channel function and activities, which canultimately lead to major pathophysiological conditions. In addition,excessive sodium influx can arise indirectly via inflammatory agents orfactors that result in hyperexcitability. Implicit with function, thisfamily of proteins are considered prime points of therapeuticintervention. Voltage-gated sodium channel proteins Na_(V)1.1 andNa_(V)1.2 are highly expressed in the brain (Raymond, C. K., et al., J.Biol. Chem. (2004), 279(44):46234-41) and are vital to normal brainfunction. In humans, mutations in Na_(V)1.1 and Na_(V)1.2 result inepileptic states and in some cases mental decline and migraines (Rhodes,T. H., et al., Proc. Natl. Acad. Sci. USA (2004),101(30):11147-52;Kamiya, K., et al., J. Biol. Chem. (2004), 24(11):2690-8; Pereira, S.,et al., Neurology (2004), 63(1):191-2; Meisler, M. H. et al., J.Physiol. (Lond.) (in press). As such both channels have been consideredas validated targets for the treatment of epilepsy (see PCT PublishedPatent Publication No. WO 01/38564).

Na_(V)1.3 is expressed primarily in the central nervous system inneonatal animals and at low levels throughout the body in adults(Raymond, C. K., et al., op. cit.). It has been demonstrated to have itsexpression upregulated in the dorsal horn sensory neurons of rats afternervous system injury (Hains, B. D., et al., J. Neurosci. (2003),23(26):8881-92). Many experts in the field have considered Na_(V)1.3 asa suitable target for pain therapeutics because its expression isinduced by nerve injury (Lai, J., et al., Curr. Opin. Neurobiol. (2003),(3):291-72003; Wood, J. N., et al., J. Neurobiol. (2004), 61(1):55-71;Chung, J. M., et al., Novartis Found Symp. (2004), 261:19-27; discussion27-31, 47-54; Priest, B. T., Curr. Opin. Drug Discov. Devel. (2009)12:682-693).

Na_(V)1.4 expression is essentially limited to muscle (Raymond, C. K.,et al., op. cit.). Mutations in this gene have been shown to haveprofound effects on muscle function including paralysis (Tamaoka A.,Intern. Med. (2003), (9):769-70). Thus, this channel is considered atarget for the treatment of periodic paralysis, myotonia, abnormalmuscle contractility, spasm or paralysis.

The cardiac voltage-gated sodium channel, Na_(V)1.5, is expressed mainlyin cardiac myocytes (Raymond, C. K., et al., op. cit.), and can be foundin the atria, ventricles, sino-atrial node, atrio-ventricular node andPurkinje cells. The rapid upstroke of the cardiac action potential andthe rapid impulse conduction through cardiac tissue is due to theopening of Na_(V)1.5. As such, Na_(V)1.5 is involved in cardiacarrhythmias. Mutations in human Na_(V)1.5 result in multiple arrhythmicsyndromes, including, for example, long QT3 (LQT3), Brugada syndrome(BS), an inherited cardiac conduction defect, sudden unexpectednocturnal death syndrome (SUNDS) and sudden infant death syndrome (SIDS)(Liu, H. et al., Am. J. Pharmacogenomics (2003), 3(3):173-9; Ruan, Y etal., Nat. Rev. Cardiol. (2009) δ: 337-48). Voltage-gated sodium channelblocker therapy has been used extensively in treating cardiacarrhythmias. The first antiarrhythmic drug, quinidine, discovered in1914, is classified as a sodium channel blocker.

Na_(V)1.6 encodes an abundant, widely distributed voltage-gated sodiumchannel found throughout the central and peripheral nervous systems,clustered in the nodes of Ranvier of neural axons (Caldwell, J. H., etal., Proc. Natl. Acad. Sci. USA (2000), 97(10): 5616-20). Loss offunction mutations in mice result in ataxia and convulsions (Papale, L.A. et al., Human Mol. Genetics. (2009) 18, 1633-1641). Although nomutations in humans have been detected, Na_(V)1.6 is thought to play arole in the manifestation of the symptoms associated with multiplesclerosis and has been considered as a target for the treatment of thisdisease (Craner, M. J., et al., Proc. Natl. Acad. Sci. USA (2004),101(21):8168-73).

Na_(V)1.7 is expressed primarily in the peripheral nervous system inboth sensory and sympathetic neurons (Raymond, C. K., et al., op. cit.).Loss of function mutations in humans cause congenital indifference topain (CIP) without impairment of cognitive or motor function (Cox, J. J.et al., Nature (2006) 444 (7121), 894-8; Goldberg, Y. P. et al., Clin.Genet. (2007) 71 (4), 311-9). Individuals with CIP do not experienceinflammatory or neuropathic pain, suggesting that selective block ofNa_(V)1.7 would eliminate multiple forms of chronic and acute painwithout deleterious effect on the central or peripheral nervous systemsor on muscle. Moreover, a single nucleotide polymorphism (R1150W) thathas very subtle effects on the time- and voltage-dependence of Na_(V)1.7gating has large effects on pain perception (Reimann, F. et al., Proc.Natl. Acad. Sci. USA (2010), 107 (11), 5148-53). About 10% of thepatients with a variety of pain conditions are heterozygous for theallele conferring greater sensitivity to pain. The involvement ofNa_(V)1.7 in mediating pain responses is also evidenced by gain offunction mutations that result in erythromelalgia or Paroxysmal extremepain disorder (Dib-Hajj S. D. et al., Adv. Genet. (2009) 63: 85-110).Although Na_(V)1.7 is expressed primarily in the peripheral nervoussystem, a point mutation in Na_(V)1.7 causes febrile seizures,indicating a role for this channel in the CNS. Thus, voltage-gatedsodium channel blockers may be useful as anticonvulsant agents.

The expression of Na_(V)1.8 is predominately in the dorsal root ganglia(DRG) (Raymond, C. K., et al., op. cit.). The upstroke of the actionpotential in sensory neurons from DRG is primarily carried by currentthrough Na_(V)1.8, so that block of this current is likely to block painresponses (Blair, N T and Bean, B P, J. Neurosci. 22: 10277-90).Consistent with this finding, knock-down of Na_(V)1.8 in rats has beenachieved by using antisense DNA or small interfering RNAs and virtuallycomplete reversal of neuropathic pain was achieved in the spinal nerveligation and chronic constriction injury models. A selective blocker ofNa_(V)1.8 has been reported and it is effective at blocking bothneuropathic and inflammatory pain (Jarvis, M. F. et al., Proc. Natl.Acad. Sci USA (2007), 104 (20), 8520-5). PCT Published PatentApplication No. WO03/037274A2 describes pyrazole-amides and sulfonamidesfor the treatment of central or peripheral nervous system conditions,particularly pain and chronic pain by blocking sodium channelsassociated with the onset or recurrance of the indicated conditions. PCTPublished Patent Application No. WO03/037890A2 describes piperidines forthe treatment of central or peripheral nervous system conditions,particularly pain and chronic pain by blocking sodium channelsassociated with the onset or recurrence of the indicated conditions. Thecompounds, compositions and methods of these inventions are ofparticular use for treating neuropathic or inflammatory pain by theinhibition of ion flux through a channel that includes a PN3 (Na_(V)1.8)subunit.

The peripheral nervous system voltage-gated sodium channel Na_(V)1.9,disclosed by Dib-Hajj, S. D., et al. (see Dib-Hajj, S. D., et al., Proc.Natl. Acad. Sci. USA (1998), 95(15):8963-8) was shown to be expressed inthe dorsal root ganglia. It has been demonstrated that Na_(V)1.9underlies neurotrophin (BDNF)-evoked depolarization and excitation. Thelimited pattern of expression of this channel has made it a candidatetarget for the treatment of pain (Lai, J, et al., op. cit.; Wood, J. N.,et al., op. cit.; Chung, J. M. et al., op. cit.).

NaX is a putative sodium channel, which has not been shown to be voltagegated. In addition to expression in the lung, heart, dorsal rootganglia, and Schwann cells of the peripheral nervous system, NaX isfound in neurons and ependymal cells in restricted areas of the CNS,particularly in the circumventricular organs, which are involved inbody-fluid homeostasis (Watanabe, E., et al., J. Neurosci. (2000),20(20):7743-51). NaX-null mice showed abnormal intakes of hypertonicsaline under both water- and salt-depleted conditions. These findingssuggest that the NaX plays an important role in the central sensing ofbody-fluid sodium level and regulation of salt intake behaviour. Itspattern of expression and function suggest it as a target for thetreatment of cystic fibrosis and other related salt regulating maladies.

Studies with the voltage-gated sodium channel blocker tetrodotoxin (TTX)used to lower neuron activity in certain regions of the brain, indicateits potential use in the treatment of addiction. Drug-paired stimulielicit drug craving and relapse in addicts and drug-seeking behavior inrats. The functional integrity of the basolateral amygdala (BLA) isnecessary for reinstatement of cocaine-seeking behaviour elicited bycocaine-conditioned stimuli, but not by cocaine itself. BLA plays asimilar role in reinstatement of heroin-seeking behavior. TTX-inducedinactivation of the BLA on conditioned and heroin-primed reinstatementof extinguished heroin-seeking behaviour in a rat model (Fuchs, R. A.and See, R. E., Psychopharmacology (2002) 160(4):425-33). A subset of Cfibers mediate responses to pruritogenic agents, especially itch causedby histamine, activators of PAR-2 receptors, cholestasis, and viralinfections (Steinhoff, M. et al., J. Neurosci. 23:6176-80; Twycross, R.et al., Q. J. Med. 96: 7-26). Voltage-gated sodium channels areexpressed in and mediate C-fiber nerve impulses.

The general value of the (S)-enantiomer of the invention in modulating,especially inhibiting, the voltage-gated sodium channel ion flux can bedetermined using the assays described below in the Biological Assayssection. Alternatively, the general value of the (S)-enantiomer of theinvention in treating conditions and diseases may be established inindustry standard animal models for demonstrating the efficacy ofcompounds in treating pain. Animal models of human neuropathic painconditions have been developed that result in reproducible sensorydeficits (allodynia, hyperalgesia, and spontaneous pain) over asustained period of time that can be evaluated by sensory testing. Byestablishing the degree of mechanical, chemical, and temperature inducedallodynia and hyperalgesia present, several physiopathologicalconditions observed in humans can be modeled allowing the evaluation ofpharmacotherapies.

In rat models of peripheral nerve injury, ectopic activity in theinjured nerve correlates with the behavioural signs of pain. In thesemodels, intravenous application of the (S)-enantiomer of the inventionand local anesthetic lidocaine can suppress the ectopic activity andreverse the tactile allodynia at concentrations that do not affectgeneral behaviour and motor function (Mao, J. and Chen, L. L, Pain(2000), 87:7-17). Allimetric scaling of the doses effective in these ratmodels, translates into doses similar to those shown to be efficaciousin humans (Tanelian, D. L. and Brose, W. G., Anesthesiology (1991),74(5):949-951). Furthermore, Lidoderm®, lidocaine applied in the form ofa dermal patch, is currently an FDA approved treatment for post-herpeticneuralgia (Devers, A. and Glaler, B. S., Clin. J. Pain (2000),16(3):205-8).

Voltage-gated sodium channel blockers have clinical uses in addition topain. Epilepsy and cardiac arrhythmias are often targets of sodiumchannel blockers. Recent evidence from animal models suggest thatvoltage-gated sodium channel blockers may also be useful forneuroprotection under ischaemic conditions caused by stroke or neuraltrauma and in patients with multiple sclerosis (MS) (Clare, J. J. etal., op. cit. and Anger, T. et al., op. cit.).

The (S)-enantiomer of the invention modulates, preferably inhibits, ionflux through a voltage-gated sodium channel in a mammal, especially in ahuman. Any such modulation, whether it be partial or complete inhibitionor prevention of ion flux, is sometimes referred to herein as “blocking”and corresponding compounds as “blockers” or “inhibitors”. In general,the compound of the invention modulates the activity of a voltage-gatedsodium channel downwards, inhibits the voltage-dependent activity of thevoltage-gated sodium channel, and/or reduces or prevents sodium ion fluxacross a cell membrane by preventing voltage-gated sodium channelactivity such as ion flux.

The (S)-enantiomer of the invention is a sodium channel blocker and istherefore useful for treating diseases and conditions in mammals,preferably in humans, and other organisms, including all those humandiseases and conditions which are the result of aberrant voltage-gatedsodium channel biological activity or which may be ameliorated oralleviated by modulation, preferably inhibition, of voltage-gated sodiumchannel biological activity.

As defined herein, a disease or condition which is ameliorated oralleviated by the modulation, preferably inhibition of a voltage-gatedsodium channel refers to a disease or condition which is ameliorated oralleviated upon the modulation, preferably inhibition, of thevoltage-gated sodium channel and includes, but is not limited to, painand pruritis; central nervous conditions such as epilepsy, anxiety,depression (Morinville et al., J. Comp. Neurol., 504:680-689 (2007)) andbipolar disease (Ettinger and Argoff, Neurotherapeutics, 4:75-83(2007)); cardiovascular conditions such as arrhythmias, atrialfibrillation and ventricular fibrillation; neuromuscular conditions suchas restless leg syndrome and muscle paralysis or tetanus;neuroprotection against stroke, neural trauma and multiple sclerosis;and channelopathies such as erythromelalgia and familial rectal painsyndrome.

Additional diseases and conditions include pain associated with HIV, HIVtreatment induced neuropathy, trigeminal neuralgia, glossopharyngealneuralgia, neuropathy secondary to metastatic infiltration, adiposisdolorosa, thalamic lesions, hypertension, autoimmune disease, asthma,drug addiction (e.g. opiate, benzodiazepine, amphetamine, cocaine,alcohol, butane inhalation), Alzheimer's (Kim DY, Carey et al., Nat.Cell Biol. 9(7):755-764 (2007)), dementia, age-related memoryimpairment, Korsakoff syndrome, restenosis, urinary dysfunction,incontinence, parkinson's disease (Do and Bean, Neuron 39:109-120(2003); Puopolo et al., J. Neurosci. 27:645-656 (2007)), cerebrovascularischemia, neurosis, gastrointestinal disease, sickle cell anemia, sicklecell disease, transplant rejection, heart failure, myocardialinfarction, reperfusion injury, intermittant claudication, angina,convulsion, respiratory disorders, cerebral or myocardial ischemias,long-QT syndrome, Catecholeminergic polymorphic ventricular tachycardia,ophthalmic diseases, spasticity, spastic paraplegia, myopathies,myasthenia gravis, paramyotonia congentia, hyperkalemic periodicparalysis, hypokalemic periodic paralysis, alopecia, anxiety disorders,psychotic disorders, mania, paranoia, seasonal affective disorder, panicdisorder, obsessive compulsive disorder (OCD), phobias, autism,Aspergers Syndrome, Retts syndrome, disintegrative disorder, attentiondeficit disorder, aggressivity, impulse control disorders, thrombosis,pre clampsia, congestive cardiac failure, cardiac arrest, Freidrich'sataxia, Spinocerebellear ataxia, tremor, muscle weakness, myelopathy,radiculopathy, systemic lupus erythamatosis, granulomatous disease,olivo-ponto-cerebellar atrophy, spinocerebellar ataxia, episodic ataxia,myokymia, progressive pallidal atrophy, progressive supranuclear palsyand spasticity, traumatic brain injury, cerebral oedema, hydrocephalusinjury, spinal cord injury, anorexia nervosa, bulimia, Prader-Willisyndrome, obesity, optic neuritis, cataract, retinal haemorrhage,ischaemic retinopathy, retinitis pigmentosa, acute and chronic glaucoma,macular degeneration, retinal artery occlusion, Chorea, Huntington'sdisease, Huntington's chorea, cerebral edema, proctitis, post-herpeticneuralgia, eudynia, heat sensitivity, sarcoidosis, irritable bowelsyndrome, Tourette syndrome, Lesch-Nyhan Syndrome, Brugado syndrome,Liddle syndrome, Crohns disease, multiple sclerosis and the painassociated with multiple sclerosis (MS), amyotrophic lateral sclerosis(ALS), disseminated sclerosis, diabetic neuropathy, peripheralneuropathy, charcot marie tooth syndrome, arthritis, rheumatoidarthritis, osteoarthritis, chondrocalcinosis, paroxysmal dystonia,myasthenia syndromes, myotonia, myotonic dystrophy, muscular dystrophy,malignant hyperthermia, cystic fibrosis, pseudoaldosteronism,rhabdomyolysis, mental handicap, bipolar depression, anxiety,schizophrenia, sodium channel toxin related illnesses, familialerythromelalgia, primary erythromelalgia, rectal pain, cancer, epilepsy,partial and general tonic seizures, febrile seizures, absence seizures(petit mal), myoclonic seizures, atonic seizures, clonic seizures,Lennox Gastaut, West Syndome (infantile spasms), sick sinus syndrome(Haufe V, Chamberland C, Dumaine R, J. Mol. Cell Cardiol. 42(3):469-477(2007)), multiresistant seizures, seizure prophylaxis(anti-epileptogenic), familial Mediterranean fever syndrome, gout,restless leg syndrome, arrhythmias, fibromyalgia, neuroprotection underischaemic conditions caused by stroke or neural trauma,tachy-arrhythmias, atrial fibrillation and ventricular fibrillation andas a general or local anaesthetic.

As used herein, the term “pain” refers to all categories of pain,regardless of its nature or origin, and is understood to include, butnot limited to, neuropathic pain, inflammatory pain, nociceptive pain,idiopathic pain, neuralgic pain, orofacial pain, burn pain, chronic bonepain, low back pain, neck pain, abdominal pain, burning mouth syndrome,somatic pain, visceral pain (including abdonminal), myofacial pain,dental pain, cancer pain, chemotherapy pain, myofascial pain syndrome,complex regional pain syndrome (CRPS), temporomandibular joint pain,trauma pain, Paroxysmal Extreme Pain Disorder, surgical pain,post-surgical pain, childbirth pain, labor pain, reflex sympatheticdystrophy, brachial plexus avulsion, neurogenic bladder, acute pain,musculoskeletal pain, post-operative pain, chronic pain, persistentpain, peripherally mediated pain, centrally mediated pain, chronicheadache, tension headache, cluster headache, migraine headache,familial hemiplegic migraine, conditions associated with cephalic pain,sinus headache, tension headache, phantom limb pain, peripheral nerveinjury, pain following stroke, thalamic lesions, radiculopathy, HIVpain, post-herpetic pain, non-cardiac chest pain, irritable bowelsyndrome and pain associated with bowel disorders and dyspepsia, andcombinations thereof.

The present invention also relates to compounds, pharmaceuticalcompositions and methods of using the compounds and pharmaceuticalcompositions for the treatment or prevention of diseases or conditionssuch as benign prostatic hyperplasia (BPH), hypercholesterolemia, cancerand pruritis (itch).

Benign prostatic hyperplasia (BPH), also known as benign prostatichypertrophy, is one of the most common diseases affecting aging men. BPHis a progressive condition which is characterized by a nodularenlargement of prostatic tissue resulting in obstruction of the urethra.Consequences of BPH can include hypertrophy of bladder smooth muscle, adecompensated bladder, acute urinary retention and an increasedincidence of urinary tract infection.

BPH has a high public health impact and is one of the most commonreasons for surgical intervention among elderly men. Attempts have beenmade to clarify the etiology and pathogenesis and, to that end,experimental models have been developed. Spontaneous animal models arelimited to the chimpanzee and the dog. BPH in man and the dog share manycommon features. In both species, the development of BPH occursspontaneously with advanced age and can be prevented byearly/prepubertal castration. A medical alternative to surgery is verydesirable for treating BHP and the consequences.

The prostatic epithelial hyperplasia in both man and the dog is androgensensitive, undergoing involution with androgen deprivation and resumingepithelial hyperplasia when androgen is replaced. Cells originating fromthe prostate gland have been shown to express high levels of voltagegated sodium channels. Immunostaining studies clearly demonstratedevidence for voltage gated sodium channels in prostatic tissues(Prostate Cancer Prostatic Dis. 2005; 8(3):266-73). Inhibiton ofvoltage-gated sodium channel function with tetrodotoxin, a selectiveblocker, inhibits migration of cells derived from prostate and breastcancers (Brackenbury, W. J. and Djamgoz, M. B. A., J. Physiol. (Lond)(2006) 573: 343-56; Chioni, A-M. et al., Int. J. Biochem. Cell Biol.(2009) 41: 1216-1227).

Hypercholesterolemia, i.e., elevated blood cholesterol, is anestablished risk factor in the development of, e.g., atherosclerosis,coronary artery disease, hyperlipidemia, stroke, hyperinsulinemias,hypertension, obesity, diabetes, cardiovascular diseases (CVD),myocardial ischemia, and heart attack. Thus, lowering the levels oftotal serum cholesterol in individuals with high levels of cholesterolhas been known to reduce the risk of these diseases. The lowering of lowdensity lipoprotein cholesterol in particular is an essential step inthe prevention of CVD. Although there are a variety ofhypercholesterolemia therapies, there is a continuing need and acontinuing search in this field of art for alternative therapies.

The invention provides compounds which are useful asantihypercholesterolemia agents and their related conditions. Thepresent compounds may act in a variety of ways. While not wishing to bebound to any particular mechanism of action, the compounds may be director indirect inhibitors of the enzyme acyl CoA: cholesterol acyltransferase (ACAT) that results in inhibition of the esterification andtransport of cholesterol across the intestinal wall. Another possibilitymay be that the compounds of the invention may be direct or indirectinhibitors of cholesterol biosynthesis in the liver. It is possible thatsome compounds of the invention may act as both direct or indirectinhibitors of ACAT and cholesterol biosynthesis.

Pruritis, commonly known as itch, is a common dermatological condition.There exist two broad categories of itch based upon the etiology:inflammatory skin itch and neuropathic itch (Binder et al., NatureClinical Practice, 4:329-337, 2008). In the former case, inflammatorymediators activate cutaneous pruriceptors, a subset of dermal afferentnerve fibers, primarily unmyelinated C fibers. Treatments for this typeof itch consist of either blocking receptors for the inflammatory agents(such as anti-histamines) or blocking the ensuing electrical activity.Voltage-gated sodium channels have a central role in the transmission ofelectrical activity in neurons and modulation of voltage-gated sodiumchannels is a well established means of modulating this signalling.Although the causes of neuropathic pruritis are complex and less wellunderstood, there is well established evidence of central sensitizationand hypersensitivity of input from sensory neuron C fibers in thedermis. As for inflammatory itch, sodium channels likely are essentialfor propagating electrical signals from the skin to the CNS.Transmission of the itch impulses results in the unpleasant sensationthat elicits the desire or reflex to scratch.

Both inflammatory and neuropathic itch can be blocked by knownvoltage-gated sodium channel blockers, most commonly lidocaine (Villamilet al., American Journal of Medicine 118:1160-1163, 2005; Inan et al.,Euorpean Journal of Pharmacology 616: 141-146, 2009; Fishman et al.,American Journal of Medicine 102: 584-585, 1997; Ross et al., Neuron 65:886-898, 2010). The doses of lidocaine needed to relieve itch arecomparable to those effective in treating pain. Both sensory circuitsshare common mediators and related neuronal pathways (Ikoma et al.,Nature Reviews Neuroscience, 7:535-547, 2006). However, other treatmentsfor pain are ineffective against itch and can exacerbate pruritis ratherthan relieve it. For example, opioids, in particular, are effective atrelieving pain, yet can generate severe pruritis. Thus, voltage-gatedsodium channel block is a particularly promising therapy for both painand itch.

Compounds of the present invention have been shown to have analgesiceffects in a number of animal models at oral doses ranging from 1 mg/Kgto 100 mg/Kg. The compounds of the invention can also be useful fortreating pruritis.

The types of itch or skin irritation, include, but are not limited to:

a) psoriatic pruritis, itch due to hemodyalisis, aguagenic pruritis, anditching caused by skin disorders (e.g., contact dermatitis), systemicdisorders, neuropathy, psychogenic factors or a mixture thereof;

b) itch caused by allergic reactions, insect bites, hypersensitivity(e.g., dry skin, acne, eczema, psoriasis), inflammatory conditions orinjury;

c) itch associated with vulvar vestibulitis;

d) skin irritation or inflammatory effect from administration of anothertherapeutic such as, for example, antibiotics, antivirals andantihistamines; and

e) itch due to activation of PAR-2 G-protein coupled receptors.

The (S)-enantiomer of the invention modulates, preferably inhibits, theion flux through a voltage-dependent sodium channel. Preferably, the(S)-enantiomer of the invention is a state- or frequency-dependentmodifier of the voltage-gated sodium channels, having a low affinity forthe rested/closed state and a high affinity for the inactivated state.While not wishing to be bound to any particular mechanism of action, the(S)-enantiomer of the invention is likely to interact with overlappingsites located in the inner cavity of the sodium conducting pore of thechannel similar to that described for other state-dependent sodiumchannel blockers (Cestèle, S., et al., op. cit.). The (S)-enantiomer ofthe invention may also be likely to interact with sites outside of theinner cavity and have allosteric effects on sodium ion conductionthrough the channel pore.

In a preferred embodiment of the invention, the (S)-enantiomer of theinvention modulates, preferaby inhibits, the activity of Na_(V)1.7. Inanother preferred embodiment of the invention, the (S)-enantiomer of theinvention selectively modulates, preferably inhibits, the activity ofNa_(V)1.7 as compared to the modulation or inhibition of othervoltage-gated sodium channels (i.e. Na_(V)1.1 to Na_(V)1.6 and Na_(V)1.8to Na_(V)1.9). Because most other sodium channels are implicated inother important physiological processes, such as contraction andrhythmicity of the heart (Na_(V)1.5), contraction of skeletal muscle(Na_(V)1.4), and conduction of electrical activity in CNS and motorneurons (Na_(V)1.1, Na_(V)1.2 and Na_(V) 1.6), it is desirable that the(S)-enantiomer of the invention avoid significant modulation of theseother sodium channels.

Any of these consequences may ultimately be responsible for the overalltherapeutic benefit provided by the (S)-enantiomer of the invention.

Typically, a successful therapeutic agent of the invention will meetsome or all of the following criteria. Oral availability should be at orabove 20%. Animal model efficacy is less than about 0.1 μg to about 100mg/Kg body weight and the target human dose is between 0.1 μg to about100 mg/Kg body weight, although doses outside of this range may beacceptable (“mg/Kg” means milligrams of compound per kilogram of bodymass of the subject to whom it is being administered). The therapeuticindex (or ratio of toxic dose to therapeutic dose) should be greaterthan 100. The potency (as expressed by IC₅₀ value) should be less than10 μM, preferably below 1 μM and most preferably below 50 nM. The IC₅₀(“Inhibitory Concentration—50%”) is a measure of the amount of the(S)-enantiomer of the invention required to achieve 50% inhibition ofion flux through a sodium channel, over a specific time period, in anassay of the invention.

Another aspect of the invention relates to inhibiting Na_(V)1.1,Na_(V)1.2, Na_(V)1.3, Na_(V)1.4, Na_(V)1.5, Na_(V)1.6, Na_(V)1.7,Na_(V)1.8, or Na_(V)1.9 activity in a biological sample or a mammal,preferably a human, which method comprises administering to the mammal,or contacting the biological sample with, the (S)-enantiomer of theinvention or a composition comprising the (S)-enantiomer of theinvention. The term “biological sample”, as used herein, includes,without limitation, cell cultures or extracts thereof; biopsied materialobtained from a mammal or extracts thereof; and blood, saliva, urine,feces, semen, tears, or other body fluids or extracts thereof.

In addition to the foregoing uses of the (S)-enantiomer of theinvention, the compound may also be useful in the modulation, preferablyinhibition, of voltage-gated sodium channel activity in a biologicalsample for a variety of purposes that are known to one of skill in theart. Examples of such purposes include, but are not limited to, thestudy of voltage-gated sodium ion channels in biological andpathological phenomena; and the comparative evaluation of new or othervoltage-gated sodium ion channel modulators.

The (S)-enantiomer of the invention may also be used to treat non-humanmammals (i.e., veterinary methods of treatment) for diseases orconditions which are ameliorated or alleviated by the modulation,preferably inhibition, of voltage-gated sodium channels, particularlyfor the treatment of inflammation and pain. Such treatment is understoodto be of particular interest for companion mammals, such as dogs andcats.

Pharmaceutical COMPOSITIONS OF THE INVENTION AND ADMINISTRATION

The present invention also relates to pharmaceutical compositioncontaining the (S)-enantiomer of the invention. In one embodiment, thepresent invention relates to a composition comprising the (S)-enantiomerof the invention in a pharmaceutically acceptable carrier and in anamount effective to modulate, preferably inhibit, ion flux through avoltage-gated sodium channel to treat diseases, such as pain, whenadministered to an animal, preferably a mammal, most preferably a humanpatient.

Administration of the (S)-enantiomer of the invention, in pure form orin an appropriate pharmaceutical composition, can be carried out via anyof the accepted modes of administration of agents for serving similarutilities. The pharmaceutical compositions of the invention can beprepared by combining a compound of the invention with an appropriatepharmaceutically acceptable carrier, diluent or excipient, and may beformulated into preparations in solid, semi-solid, liquid or gaseousforms, such as tablets, capsules, powders, granules, ointments,solutions, suppositories, injections, inhalants, gels, microspheres, andaerosols. Typical routes of administering such pharmaceuticalcompositions include, without limitation, oral, topical, transdermal,inhalation, parenteral, sublingual, rectal, vaginal, and intranasal. Theterm parenteral as used herein includes subcutaneous injections,intravenous, intramuscular, intrasternal injection or infusiontechniques. Pharmaceutical compositions of the invention are formulatedso as to allow the active ingredients contained therein to bebioavailable upon administration of the composition to a patient.Compositions that will be administered to a subject or patient,preferably a mammal, more preferably a human, take the form of one ormore dosage units, where for example, a tablet may be a single dosageunit, and a container of a compound of the invention in aerosol form mayhold a plurality of dosage units. Actual methods of preparing suchdosage forms are known, or will be apparent, to those skilled in thisart; for example, see The Science and Practice of Pharmacy, 20th Edition(Philadelphia College of Pharmacy and Science, 2000). The composition tobe administered will, in any event, contain a therapeutically effectiveamount of a compound of the invention, or a pharmaceutically acceptablesalt thereof, for treatment of a disease or condition of interest inaccordance with the teachings of this invention.

The pharmaceutical compositions useful herein also contain apharmaceutically acceptable carrier, including any suitable diluent orexcipient, which includes any pharmaceutical agent that does not itselfinduce the production of antibodies harmful to the individual receivingthe composition, and which may be administered without undue toxicity.Pharmaceutically acceptable carriers include, but are not limited to,liquids, such as water, saline, glycerol and ethanol, and the like. Athorough discussion of pharmaceutically acceptable carriers, diluents,and other excipients is presented in REMINGTON'S PHARMACEUTICAL SCIENCES(Mack Pub. Co., N.J., current edition).

A pharmaceutical composition of the invention may be in the form of asolid or liquid. In one aspect, the carrier(s) are particulate, so thatthe compositions are, for example, in tablet or powder form. Thecarrier(s) may be liquid, with the compositions being, for example, anoral syrup, injectable liquid or an aerosol, which is useful in, forexample, inhalatory administration.

When intended for oral administration, the pharmaceutical composition ispreferably in either solid or liquid form, where semi-solid,semi-liquid, suspension and gel forms are included within the formsconsidered herein as either solid or liquid.

As a solid composition for oral administration, the pharmaceuticalcomposition may be formulated into a powder, granule, compressed tablet,pill, capsule, chewing gum, wafer or the like form. Such a solidcomposition will typically contain one or more inert diluents or ediblecarriers. In addition, one or more of the following may be present:binders such as carboxymethylcellulose, ethyl cellulose,microcrystalline cellulose, gum tragacanth or gelatin; excipients suchas starch, lactose or dextrins, disintegrating agents such as alginicacid, sodium alginate, Primogel, corn starch and the like; lubricantssuch as magnesium stearate or Sterotex; glidants such as colloidalsilicon dioxide; sweetening agents such as sucrose or saccharin; aflavoring agent such as peppermint, methyl salicylate or orangeflavoring; and a coloring agent.

When the pharmaceutical composition is in the form of a capsule, forexample, a gelatin capsule, it may contain, in addition to materials ofthe above type, a liquid carrier such as polyethylene glycol or oil.

The pharmaceutical composition may be in the form of a liquid, forexample, an elixir, syrup, solution, emulsion or suspension. The liquidmay be for oral administration or for delivery by injection, as twoexamples. When intended for oral administration, preferred compositionscontain, in addition to the (S)-enantiomer of the invention, one or moreof a sweetening agent, preservatives, dye/colorant and flavor enhancer.In a composition intended to be administered by injection, one or moreof a surfactant, preservative, wetting agent, dispersing agent,suspending agent, buffer, stabilizer and isotonic agent may be included.

The liquid pharmaceutical compositions of the invention, whether they besolutions, suspensions or other like form, may include one or more ofthe following adjuvants: sterile diluents such as water for injection,saline solution, preferably physiological saline, Ringer's solution,isotonic sodium chloride, fixed oils such as synthetic mono ordiglycerides which may serve as the solvent or suspending medium,polyethylene glycols, glycerin, propylene glycol or other solvents;antibacterial agents such as benzyl alcohol or methyl paraben;antioxidants such as ascorbic acid or sodium bisulfite; chelating agentssuch as ethylenediaminetetraacetic acid; buffers such as acetates,citrates or phosphates and agents for the adjustment of tonicity such assodium chloride or dextrose. The parenteral preparation can be enclosedin ampoules, disposable syringes or multiple dose vials made of glass orplastic. Physiological saline is a preferred adjuvant. An injectablepharmaceutical composition is preferably sterile.

A liquid pharmaceutical composition of the invention intended for eitherparenteral or oral administration should contain an amount of the(S)-enantiomer of the invention such that a suitable dosage will beobtained. Typically, this amount is at least 0.01% of the (S)-enantiomerof the invention in the composition. When intended for oraladministration, this amount may be varied to be between 0.1 and about70% of the weight of the composition. Preferred oral pharmaceuticalcompositions contain between about 4% and about 50% of the(S)-enantiomer of the invention. Preferred pharmaceutical compositionsand preparations according to the present invention are prepared so thata parenteral dosage unit contains between 0.01 to 10% by weight of the(S)-enantiomer of the invention prior to dilution.

The pharmaceutical composition of the invention may be intended fortopical administration, in which case the carrier may suitably comprisea solution, emulsion, ointment or gel base. The base, for example, maycomprise one or more of the following: petrolatum, lanolin, polyethyleneglycols, bee wax, mineral oil, diluents such as water and alcohol, andemulsifiers and stabilizers. Thickening agents may be present in apharmaceutical composition for topical administration. If intended fortransdermal administration, the composition may include a transdermalpatch or iontophoresis device. Topical formulations may contain aconcentration of the (S)-enantiomer of the invention from about 0.1 toabout 10% w/v (weight per unit volume).

For topical applications, it is preferred to administer an effectiveamount of a pharmaceutical composition according to the invention totarget area, e.g., skin surfaces, mucous membranes, and the like, whichare adjacent to peripheral neurons which are to be treated. This amountwill generally range from about 0.0001 mg to about 1 g of the(S)-enantiomer of the invention per application, depending upon the areato be treated, whether the use is diagnostic, prophylactic ortherapeutic, the severity of the symptoms, and the nature of the topicalvehicle employed. A preferred topical preparation is an ointment,wherein about 0.001 to about 50 mg of active ingredient is used per ccof ointment base. The pharmaceutical composition can be be formulated astransdermal compositions or transdermal delivery devices (“patches”).Such compositions include, for example, a backing, active compoundreservoir, a control membrane, liner and contact adhesive. Suchtransdermal patches may be used to provide continuous pulsatile, or ondemand delivery of the compounds of the present invention as desired.

The pharmaceutical composition of the invention may be intended forrectal administration, in the form, for example, of a suppository, whichwill melt in the rectum and release the drug. The composition for rectaladministration may contain an oleaginous base as a suitablenonirritating excipient. Such bases include, without limitation,lanolin, cocoa butter and polyethylene glycol.

A typical formulation for intramuscular or intrathecal administrationwill consist of a suspension or solution of active in an oil or solutionof active ingredient in an oil, for example arachis oil or sesame oil. Atypical formulation for intravenous or intrathecal administration willconsist of sterile isotonic aqueous solution containing, for exampleactive ingredient and dextrose or sodium chloride or a mixture ofdextrose and sodium chloride.

The compositions of the invention can be formulated so as to providequick, sustained or delayed release of the active ingredient, i.e, the(S)-enantiomer of the invention, after administration to the patient byemploying procedures known in the art. Controlled release drug deliverysystems include osmotic pump systems and dissolutional systemscontaining polymer-coated reservoirs or drug-polymer matrixformulations. Examples of controlled release systems are given in U.S.Pat. Nos. 3,845,770 and 4,326,525 and in P. J. Kuzma et al., RegionalAnesthesia 22 (6): 543-551 (1997), all of which are incorporated hereinby reference.

The compositions of the invention can also be delivered throughintra-nasal drug delivery systems for local, systemic, and nose-to-brainmedical therapies. Controlled Particle Dispersion (CPD)™ technology,traditional nasal spray bottles, inhalers or nebulizers are known bythose skilled in the art to provide effective local and systemicdelivery of drugs by targeting the olfactory region and paranasalsinuses.

The invention also relates to an intravaginal shell or core drugdelivery device suitable for administration to the human or animalfemale. The device may be comprised of the active pharmaceuticalingredient in a polymer matrix, surrounded by a sheath, and capable ofreleasing the (S)-enantiomer of the invention in a substantially zeroorder pattern on a daily basis similar to devises used to applytestosterone as desscribed in PCT Published Patent Application No. WO98/50016.

Current methods for ocular delivery include topical administration (eyedrops), subconjunctival injections, periocular injections, intravitrealinjections, surgical implants and iontophoresis (uses a small electricalcurrent to transportionized drugs into and through body tissues). Thoseskilled in the art would combine the best suited excipients with the(S)-enantiomer of the invention for safe and effective intra-occularadministration.

The most suitable route of administration will depend on the nature andseverity of the condition being treated. Those skilled in the art arealso familiar with determining administration methods (e.g., oral,intravenous, inhalation, sub-cutaneous, rectal etc.), dosage forms,suitable pharmaceutical excipients and other matters relevant to thedelivery of the (S)-enantiomer of the invention to a subject in needthereof.

The pharmaceutical composition of the invention may include variousmaterials, which modify the physical form of a solid or liquid dosageunit. For example, the composition may include materials that form acoating shell around the active ingredients. The materials that form thecoating shell are typically inert, and may be selected from, forexample, sugar, shellac, and other enteric coating agents.Alternatively, the active ingredients may be encased in a gelatincapsule.

The pharmaceutical composition of the invention in solid or liquid formmay include an agent that binds to the (S)-enantiomer of the inventionand thereby assists in the delivery of the compound. Suitable agentsthat may act in this capacity include a monoclonal or polyclonalantibody, a protein or a liposome.

The pharmaceutical composition of the invention may consist of dosageunits that can be administered as an aerosol. The term aerosol is usedto denote a variety of systems ranging from those of colloidal nature tosystems consisting of pressurized packages. Delivery may be by aliquefied or compressed gas or by a suitable pump system that dispensesthe active ingredients. Aerosols of the (S)-enantiomer of the inventionmay be delivered in single phase, bi-phasic, or tri-phasic systems inorder to deliver the active ingredient(s). Delivery of the aerosolincludes the necessary container, activators, valves, subcontainers, andthe like, which together may form a kit. One skilled in the art, withoutundue experimentation may determine preferred aerosols.

The pharmaceutical compositions of the invention may be prepared bymethodology well known in the pharmaceutical art. For example, apharmaceutical composition intended to be administered by injection canbe prepared by combining the (S)-enantiomer of the invention withsterile, distilled water so as to form a solution. A surfactant may beadded to facilitate the formation of a homogeneous solution orsuspension. Surfactants are compounds that non-covalently interact withthe (S)-enantiomer of the invention so as to facilitate dissolution orhomogeneous suspension of the compound in the aqueous delivery system.

The (S)-enantiomer of the invention is to be administered in atherapeutically effective amount, which will vary depending upon avariety of factors including the activity of the specific compoundemployed; the metabolic stability and length of action of the(S)-enantiomer of the invention; the age, body weight, general health,sex, and diet of the patient; the mode and time of administration; therate of excretion; the drug combination; the severity of the particulardisorder or condition; and the subject undergoing therapy. Generally, atherapeutically effective daily dose of the (S)-enantiomer of theinvention is (for a 70 Kg mammal) from about 0.001 mg/Kg (i.e., 0.07 mg)to about 100 mg/Kg (i.e., 7.0 g); preferably a therapeutically effectivedose is (for a 70 Kg mammal) from about 0.01 mg/Kg (i.e., 0.70 mg) toabout 50 mg/Kg (i.e., 3.5 g); and more preferably a therapeuticallyeffective dose is (for a 70 Kg mammal) from about 1 mg/Kg (i.e., 70 mg)to about 25 mg/Kg (i.e., 1.75 g).

The ranges of effective doses provided herein are not intended to belimiting and represent preferred dose ranges. However, the mostpreferred dosage will be tailored to the individual subject, as isunderstood and determinable by one skilled in the relevant arts. (see,e.g., Berkowet at., eds., The Merck Manual, 16^(th) edition, Merck andCo., Rahway, N.J., 1992; Goodmanetna., eds., Goodman and Cilman's ThePharmacological Basis of Therapeutics, 10^(th) edition, Pergamon Press,Inc., Elmsford, N.Y., (2001); Avery's Drug Treatment: Principles andPractice of Clinical Pharmacology and Therapeutics, 3rd edition, ADISPress, LTD., Williams and Wilkins, Baltimore, Md. (1987), Ebadi,Pharmacology, Little, Brown and Co., Boston, (1985); Osolci al., eds.,Remington's Pharmaceutical Sciences, 18^(th) edition, Mack PublishingCo., Easton, Pa. (1990); Katzung, Basic and Clinical Pharmacology,Appleton and Lange, Norwalk, Conn. (1992)).

The total dose required for each treatment can be administered bymultiple doses or in a single dose over the course of the day, ifdesired. Generally, treatment is initiated with smaller dosages, whichare less than the optimum dose of the compound. Thereafter, the dosageis increased by small increments until the optimum effect under thecircumstances is reached. The diagnostic pharmaceutical compound orcomposition can be administered alone or in conjunction with otherdiagnostics and/or pharmaceuticals directed to the pathology, ordirected to other symptoms of the pathology. Effective amounts of the(S)-enantiomer of the invention or composition of the invention are fromabout 0.1 μg to about 100 mg/Kg body weight, administered at intervalsof 4-72 hours, for a period of 2 hours to 1 year, and/or any range orvalue therein, such as 0.0001-0.001, 0.001-0.01, 0.01-0.1, 0.1-1.0,1,0-10, 5-10, 10-20, 20-50 and 50-100 mg/Kg, at intervals of 1-4, 4-10,10-16, 16-24, 24-36, 24-36, 36-48, 48-72 hours, for a period of 1-14,14-28, or 30-44 days, or 1-24 weeks, or any range or value therein.

The recipients of administration of the (S)-enantiomer of the inventionand/or compositions of the invention can be any animal, such as mammals.Among mammals, the preferred recipients are mammals of the OrdersPrimate (including humans, apes and monkeys), Arteriodactyla (includinghorses, goats, cows, sheep, pigs), Rodenta (including mice, rats,rabbits, and hamsters), and Carnivora (including cats, and dogs). Amongbirds, the preferred recipients are turkeys, chickens and other membersof the same order. The most preferred recipients are humans.

Combination Therapy

The (S)-enantiomer of the invention may be usefully combined with one ormore other therapeutic agent or as any combination thereof, in thetreatment of diseases and conditions in mammals, preferably humans,which are ameliorated or alleviated by the modulation, preferablyinhibition, of voltage-gated sodium channels. For example, the(S)-enantiomer of the invention may be administered simultaneously,sequentially or separately in combination with other therapeutic agents,including, but not limited to:

-   -   opiates analgesics, e.g. morphine, heroin, cocaine, oxymorphine,        levorphanol, levallorphan, oxycodone, codeine, dihydrocodeine,        propoxyphene, nalmefene, fentanyl, hydrocodone, hydromorphone,        meripidine, methadone, nalorphine, naloxone, naltrexone,        buprenorphine, butorphanol, nalbuphine and pentazocine;    -   non-opiate analgesics, e.g. acetomeniphen, salicylates (e.g.        aspirin);    -   nonsteroidal antiinflammatory drugs (NSAIDs), e.g. ibuprofen,        naproxen, fenoprofen, ketoprofen, celecoxib, diclofenac,        diflusinal, etodolac, fenbufen, fenoprofen, flufenisal,        flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac,        meclofenamic acid, mefenamic acid, meloxicam, nabumetone,        naproxen, nimesulide, nitroflurbiprofen, olsalazine, oxaprozin,        phenylbutazone, piroxicam, sulfasalazine, sulindac, tolmetin and        zomepirac;    -   anticonvulsants, e.g. carbamazepine, oxcarbazepine, lamotrigine,        valproate, topiramate, gabapentin and pregabalin;    -   antidepressants such as tricyclic antidepressants, e.g.        amitriptyline, clomipramine, despramine, imipramine and        nortriptyline;    -   COX-2 selective inhibitors, e.g. celecoxib, rofecoxib,        parecoxib, valdecoxib, deracoxib, etoricoxib, and lumiracoxib;    -   alpha-adrenergics, e.g. doxazosin, tamsulosin, clonidine,        guanfacine, dexmetatomidine, modafinil, and        4-amino-6,7-dimethoxy-2-(5-methane        sulfonamido-1,2,3,4-tetrahydroisoquinol-2-yl)-5-(2-pyridyl)quinazoline;    -   barbiturate sedatives, e.g. amobarbital, aprobarbital,        butabarbital, butabital, mephobarbital, metharbital,        methohexital, pentobarbital, phenobartital, secobarbital,        talbutal, theamylal and thiopental;    -   tachykinin (NK) antagonist, particularly an NK-3, NK-2 or NK-1        antagonist, e.g.        (αR,9R)-7-[3,5-bis(trifluoromethyl)benzyl)]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H-[1,4]diazocino[2,1-g][1,7]-naphthyridine-6-13-dione        (TAK-637),        5-[[2R,3S)-2-[(1R)-1-[3,5-bis(trifluoromethylphenyl]ethoxy-3-(4-fluorophenyl)-4-morpholinyl]-methyl]-1,2-dihydro-3H-1,2,4-triazol-3-one        (MK-869), aprepitant, lanepitant, dapitant or        3-[[2-methoxy5-(trifluoromethoxy)phenyl]-methylamino]-2-phenylpiperidine        (2S,3S);    -   coal-tar analgesics, in particular paracetamol;    -   serotonin reuptake inhibitors, e.g. paroxetine, sertraline,        norfluoxetine (fluoxetine desmethyl metabolite), metabolite        demethylsertraline, ′3 fluvoxamine, paroxetine, citalopram,        citalopram metabolite desmethylcitalopram, escitalopram,        d,l-fenfluramine, femoxetine, ifoxetine, cyanodothiepin,        litoxetine, dapoxetine, nefazodone, cericlamine, trazodone and        fluoxetine;    -   noradrenaline (norepinephrine) reuptake inhibitors, e.g.        maprotiline, lofepramine, mirtazepine, oxaprotiline, fezolamine,        tomoxetine, mianserin, buproprion, buproprion metabolite        hydroxybuproprion, nomifensine and viloxazine (Vivalan®)),        especially a selective noradrenaline reuptake inhibitor such as        reboxetine, in particular (S,S)-reboxetine, and venlafaxine        duloxetine neuroleptics sedative/anxiolytics;    -   dual serotonin-noradrenaline reuptake inhibitors, such as        venlafaxine, venlafaxine metabolite O-desmethylvenlafaxine,        clomipramine, clomipramine metabolite desmethylclomipramine,        duloxetine, milnacipran and imipramine;    -   acetylcholinesterase inhibitors such as donepezil;    -   5-HT3 antagonists such as ondansetron;    -   metabotropic glutamate receptor (mGluR) antagonists or agonists        or allosteric potentiators of glutamate at mGluR's;    -   local anaesthetic such as mexiletine and lidocaine;    -   corticosteroid such as dexamethasone;    -   antiarrhythimics, e.g. mexiletine and phenyloin;    -   muscarinic antagonists, e.g., tolterodine, propiverine, tropsium        t chloride, darifenacin, solifenacin, temiverine and        ipratropium;    -   muscarinic agonists or allosteric potentiators of acetylcholine        at muscarinic receptors    -   cannabinoids or allosteric potentiators of endorphins at        cannabinoid receptors;    -   vanilloid receptor agonists (e.g. resinferatoxin) or antagonists        (e.g. capsazepine);    -   sedatives, e.g. glutethimide, meprobamate, methaqualone, and        dichloralphenazone;    -   anxiolytics such as benzodiazepines,    -   antidepressants such as mirtazapine,    -   topical agents (e.g. lidocaine, capsacin and resiniferotoxin);    -   muscle relaxants such as benzodiazepines, baclofen,        carisoprodol, chlorzoxazone, cyclobenzaprine, methocarbamol and        orphrenadine;    -   anti-histamines or H1 antagonists;    -   NMDA receptor antagonists;    -   5-HT receptor agonists/antagonists;    -   PDEV inhibitors;    -   Tramadol®;    -   cholinergic (nicotinic) analgesics;    -   alpha-2-delta ligands;    -   prostaglandin E2 subtype antagonists;    -   leukotriene B4 antagonists;    -   5-lipoxygenase inhibitors; and    -   5-HT3 antagonists.

Diseases and conditions that may be treated and/or prevented using suchcombinations include, but are not limited to, pain, central andperipherally mediated, acute, chronic, neuropathic diseases, as well asother diseases with associated pain and other central nervous disorderssuch as epilepsy, anxiety, depression and bipolar disease; orcardiovascular disorders such as arrhythmias, atrial fibrillation andventricular fibrillation; neuromuscular disorders such as restless legsyndrome and muscle paralysis or tetanus (Hamann M, Meisler M H,Richter, A Exp. Neurol. 184(2):830-838 (2003)); neuroprotection againststroke, neural trauma and multiple sclerosis; and channelopathies suchas erythromelalgia and familial rectal pain syndrome.

As used herein “combination” refers to any mixture or permutation of the(S)-enantiomer of the invention with one or more additional therapeuticagent. Unless the context makes clear otherwise, “combination” mayinclude simultaneous or sequentially delivery of the (S)-enantiomer ofthe invention with one or more therapeutic agents. Unless the contextmakes clear otherwise, “combination” may include dosage forms of the(S)-enantiomer of the invention with another therapeutic agent. Unlessthe context makes clear otherwise, “combination” may include routes ofadministration of the (S)-enantiomer of the invention with anothertherapeutic agent. Unless the context makes clear otherwise,“combination” may include formulations of the (S)-enantiomer of theinvention with another therapeutic agent. Dosage forms, routes ofadministration and pharmaceutical compositions include, but are notlimited to, those described herein.

One combination therapy of the invention includes a topical applicationof the (S)-enantiomer of the invention with an oral agent. The topicalapplication of the (S)-enantiomer of the invention has very low systemicexposure and has activity that is additive with a number of oralanalgesics. Another possible combination therapy includes an oral doseof the (S)-enantiomer of the invention with an oral agent. A furthercombination therapy of the invention includes a topical application ofthe (S)-enantiomer of the invention with a topical agent.

The (S)-enantiomer of the invention may be incorporated intocompositions for coating an implantable medical device, such asprostheses, artifical valves, vascular grafts, stents and catheters.Accordingly, the present invention, in another aspect, includes acomposition for coating an implantable device comprising a compound ofthe present invention as described above and a carrier suitable forcoating the implantable device. In still another aspect, the presentinvention includes an implantable device coated with a compositioncomprising the (S)-enantiomer of the invention and a carrier suitablefor coating the implantable device. Suitable coatings and the generalpreparation of coated implantable devices are described in U.S. Pat.Nos. 6,099,562; 5,886,026; and 5,304,121.

Kits-of-Parts

The present invention also provides kits that contain a pharmaceuticalcomposition of the invention. The kit also includes instructions for theuse of the pharmaceutical composition for modulating the activity of ionchannels, for the treatment of pain, as well as other utilities asdisclosed herein. Preferably, a commercial package will contain one ormore unit doses of the pharmaceutical composition. For example, such aunit dose may be an amount sufficient for the preparation of anintravenous injection. It will be evident to those of ordinary skill inthe art that such compositions which are light and/or air sensitive mayrequire special packaging and/or formulation. For example, packaging maybe used which is opaque to light, and/or sealed from contact withambient air, and/or formulated with suitable coatings or excipients.

Preparation of the (S)-Enantiomer of the Invention

The (S)-enantiomer of the invention and the corresponding (R)-enantiomerare prepared by the resolution of the compound of formula (I), as setforth above in the Summary of the Invention, using either chiral highpressure liquid chromatography methods or by simulated moving bedchromatography methods, as described below in the following ReactionScheme wherein “chiral HPLC” refers to chiral high pressure liquidchromatography and “SMB” refers to simulated moving bed chromatography:

The compound of formula (I) can be prepared by the methods disclosed inPCT Published Patent Application No. WO 2006/110917, by methodsdisclosed herein, or by methods known to one skilled in the art.

One of ordinary skill in the art would recognize variations in the aboveReaction Scheme which are appropriate for the resolution of theindividual enantiomers.

Alternatively, the (S)-enantiomer of formula (I-S) and the(R)-enantiomer of formula (I-R), can be synthesized from startingmaterials which are known or readily prepared using process analogous tothose which are known.

Preferably, the (S)-enantiomer of the invention obtained by theresolution methods disclosed herein is substantially free of the(R)-enantiomer or contains only traces of the (R)-enantiomer.

The following Synthetic Examples serve to illustrate the resolutionmethods disclosed by the above Reaction Schemes and are not intended tolimit the scope of the invention.

Synthetic Example 1 Synthesis of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one(Compound of Formula (I))

To a suspension ofspiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (1.0 g, 3.6mmol), which can be prepared according to the methods disclosed in PCTPublished Patent Application No. WO 2006/110917, and cesium carbonate(3.52 g, 11 mmol) in acetone (50 mL) was added2-bromomethyl-5-trifluoromethylfuran (1.13 g, 3.9 mmol) in one portionand the reaction mixture was stirred at 55-60° C. for 16 hours. Uponcooling to ambient temperature, the reaction mixture was filtered andthe filtrate was evaporated under reduced pressure. The residue wassubjected to column chromatography, eluting with ethyl acetate/hexane(1/9-1/1) to afford1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one,i.e., the compound of formula (I), (1.17 g, 76%) as a white solid: mp139-141° C.; ¹H NMR (300 MHz, CDCl₃) δ 7.32-6.97 (m, 5H), 6.72 (d, J=3.3Hz, 1H), 6.66 (s, 1H), 6.07 (s, 1H), 5.90-5.88 (m, 2H), 5.05, 4.86 (ABq,J_(AB)=16.1 Hz, 2H), 4.91 (d, J=9.0 Hz, 1H), 4.66 (d, J=9.0 Hz, 1H); ¹³CNMR (75 MHz, CDCl₃) δ 176.9, 155.7, 153.5, 148.8, 142.2, 141.9, 140.8,140.2, 139.7, 139.1, 132.1, 129.2, 124.7, 124.1, 123.7, 121.1, 120.1,117.6, 114.5, 114.4, 110.3, 109.7, 103.0, 101.9, 93.8, 80.0, 57.8, 36.9;MS (ES+) m/z 430.2 (M+1), 452.2 (M+23); Cal'd for C₂₂H₁₄F₃NO₆: C,61.54%; H, 3.29%; N, 3.26%; Found: C, 61.51%; H, 3.29%; N, 3.26%.

Synthetic Example 2 Resolution of Compound of Formula (I) by Chiral HPLC

The compound of formula (I) was resolved into the (S)-enantiomer of theinvention and the corresponding (R)-enantiomer by chiral HPLC under thefollowing conditions:

-   -   Column: Chiralcel OJ-RH; 20 mm I.D.×250 mm, 5 mic; Lot: OJRH        CJ-EH001 (Daicel Chemical Industries, Ltd)    -   Eluent: AcetonitrileNVater (60/40, v/v, isocratic)    -   Flow rate: 10 mL/min    -   Run time: 60 min    -   Loading: 100 mg of compound of formula (I) in 1 mL of        acetonitrile    -   Temperature: Ambient

Under the above chiral HPLC conditions, the (R)-enantiomer of thecompound of formula (I), i.e.,(R)-1-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]-benzodioxole-7,3′-indol]-2′(1′H)-one,was isolated as the first fraction as a white solid; ee (enantiomericexcess)>99% (analytical OJ-RH, 55% acetonitrile in water); mp 103-105°C.; ¹H NMR (300 MHz, DMSO-d₆) δ 7.32-6.99 (m, 5H), 6.71 (d, J=3.4 Hz,1H), 6.67 (s, 1H), 6.05 (s, 1H), 5.89 (d, J=6.2 Hz, 2H), 5.13, 5.02(ABq, J_(AB)=16.4 Hz, 2H), 4.82, 4.72 (ABq, J_(AB)=9.4 Hz, 2H); ¹³C NMR(75 MHz, CDCl₃) δ 177.2, 155.9, 152.0, 149.0, 142.4, 142.0, 141.3,132.0, 129.1, 123.9, 120.6, 119.2, 117.0, 112.6, 109.3, 108.9, 103.0,101.6, 93.5, 80.3, 58.2, 36.9; MS (ES+) m/z 430.2 (M+1), [α]_(D) −17.46°(c 0.99, DMSO). The (S)-enantiomer of the compound of formula (I), i.e.,(S)-1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro-[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onewas isolated as the second fraction as a white solid; ee>99% (analyticalOJ-RH, 55% acetonitrile in water); mp 100-102° C.; ¹H NMR (300 MHz,DMSO-d₆) δ 7.32-6.99 (m, 5H), 6.71 (d, J=3.4 Hz, 1H), 6.67 (s, 1H), 6.05(s, 1H), 5.89 (d, J=6.3 Hz, 2H), 5.12, 5.02 (ABq, J_(AB)=16.4 Hz, 2H),4.82, 4.72 (ABq, J_(AB)=9.4 Hz, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 177.2,155.9, 152.0, 149.0, 142.4, 142.0, 141.3, 132.0, 129.1, 123.9, 120.6,119.2, 117.0, 112.6, 109.3, 108.9, 103.0, 101.6, 93.5, 80.3, 58.2, 36.9;MS (ES+) m/z 430.2 (M+1), [α]_(D) +14.04° (c 0.99, DMSO).

Synthetic Example 3 Resolution of Compound of Formula (I) by SMBChromatography

The compound of formula (I) was resolved into the (S)-enantiomer of theinvention and the corresponding (R)-enantiomer by SMB chromatographyunder the following conditions:

-   -   Extract: 147.05 mL/min    -   Raffinate: 76.13 mL/min    -   Eluent: 183.18 mL/min    -   Feed: 40 mL/min    -   Recycling: 407.88 mL/min    -   Run Time: 0.57 min    -   Temperature: 25° C.    -   Pressure: 46 bar

The feed solution (25 g of compound of formula (I) in 1.0 L of mobilephase (25:75:0.1 (v:v:v) mixture ofacetonitrile/methanol/trifluoroacetic acid)) was injected continuouslyinto the SMB system (Novasep Licosep Lab Unit), which was equipped witheight identical columns in 2-2-2-2 configuration containing 110 g (percolumn, 9.6 cm, 4.8 cm I.D.) of ChiralPAK-AD as stationary phase. Thefirst eluting enantiomer (the (R)-enantiomer of the compound of formula(I)) was contained in the raffinate stream and the second elutingenantiomer (the (S)-enantiomer of the compound of formula (I)) wascontained in the extract stream. The characterization data of the(S)-enantiomer and the (R)-enantiomer obtained from the SMB resolutionwere identical to those obtained above utilizing chiral HPLC.

The compound of formula (I) was resolved into its constituentenantiomers on a Waters preparative LCMS autopurification system. Thefirst-eluting enantiomer from the chiral column was brominated (at asite well-removed from the stereogenic centre) to give the corresponding5′-bromo derivative, which was subsequently crystallized to generate asingle crystal suitable for X-ray crystallography. The crystal structureof this brominated derivative of the first-eluting enantiomer wasobtained and its absolute configuration was found to be the same as the(R)-enantiomer of the invention. Hence, the second-eluting enantiomerfrom the chiral column is the (S)-enantiomer of the invention. Moreover,the material obtained from the extract stream of the SMB resolution hada specific optical rotation of the same sign (positive, i.e.dextrorotatory) as that of the material obtained from the aforementionedLC resolution.

Biological Assays

Various techniques are known in the art for testing the activity of thecompound of the invention or determining their solubility in knownpharmaceutically acceptable excipients. In order that the inventiondescribed herein may be more fully understood, the following biologicalassays are set forth. It should be understood that these examples arefor illustrative purposes only and are not to be construed as limitingthis invention in any manner.

Biological Example 1 Guanidine Influx Assay (In Vitro Assay)

This example describes an in vitro assay for testing and profiling testagents against human or rat voltage-gated sodium channels stablyexpressed in cells of either an endogenous or heterologously expressedorigin. The assay is also useful for determining the IC₅₀ of avoltage-gated sodium channel modulating (preferably blocking) compound.The assay is based on the guanidine influx assay described by Reddy, N.L., et al., J. Med. Chem. (1998), 41(17):3298-302.

The guanidine influx assay is a radiotracer flux assay used to determineion flux activity of voltage-gated sodium channels in a high-throughputmicroplate-based format. The assay uses ¹⁴C-guanidine hydrochloride incombination with various known voltage-gated sodium channel modulatorsthat produce maintained influx, to assay the potency of test agents.Potency is determined by an IC₅₀ calculation.

Selectivity is determined by comparing potency of the compound for thevoltage-gated sodium channel of interest to its potency against othervoltage-gated sodium channels (also called ‘selectivity profiling’).

Each of the test agents is assayed against cells that express thevoltage-gated sodium channels of interest. Voltage-gated sodium channelsare characterized as TTX sensitive or insensitive. This property isuseful when evaluating the activities of a voltage-gated sodium channelof interest when it resides in a mixed population with othervoltage-gated sodium channels. The following Table 1 summarizes celllines useful in screening for a certain voltage-gated sodium channelactivity in the presence or absence of TTX.

TABLE 1 CELL LINE mRNA Expression Functional Characterization CHO-K1(Chinese Na_(v)1.4 expression The 18- to 20-fold increase Hamster Ovary;has been shown in [¹⁴C] guanidine influx was recommended by RT-PCR Nocompletely blocked using host cell line) other Na_(v) TTX. (Na_(v)1.4 isa TTX ATTC accession expressionhas sensitive channel) number CCL-61 beendetected L6 (rat myoblast Expression of The 10- to 15-fold increasecell) ATTC Na_(v)1.4 and 1.5 in [¹⁴C] guanidine influx was NumberCRL-1458 only partially blocked by TTX at 100 nM (Na_(v)1.5 is TTXresistant) SH-SY5Y (Human Published The 10- to 16-fold increaseneuroblastoma) Expression of in [¹⁴C] guanidine influx ATTC NumberNa_(v)1.9 and Na_(v)1.7 above background was CRL-2266 (Blum et al.)partially blocked by TTX (Na_(v)1.9 is TTX resistant) SK-N-BE2C (aExpression of Stimulation of BE2C cells human Na_(v)1.8 with pyrethroidsresults in neuroblastoma cell a 6-fold increase in [¹⁴C] line ATCCNumber guanidine influx above background. CRL-2268) TTX partiallyblocked influx (Na_(v)1.8 is TTX resistant) PC12 (rat Expression of The8- to 12-fold increase in pheochromocytoma) Na_(v)1.2 and [¹⁴C]guanidine influx was ATTC Number Na_(v)1.7 completely blocked usingCRL-1721 TTX. (Na_(v)1.2 and Na_(v)1.7 are TTX sensitive channels)HEK293 (human Expression of Nav1.7 is a TTX sensitive embryonic kidney)hNa_(v)1.7 channel. The TTX IC₅₀ in the ATTC Number functionalGuanidinium assay CRL-1573 is 8 nM.

It is also possible to employ immortalized cell lines thatheterologously express voltage-gated sodium channels. Cloning, stabletransfection and propagation of such cell lines are known to thoseskilled in the art (see, for example, Klugbauer, N, et al., EMBO J.(1995), 14(6):1084-90; and Lossin, C., et al., Neuron (2002), 34, pp.877-884).

Cells expressing the voltage-gated sodium channel of interest are grownaccording to the supplier or in the case of a recombinant cell in thepresence of selective growth media such as G418 (Gibco/Invitrogen). Thecells are disassociated from the culture dishes with an enzymaticsolution (1×) Trypsin/EDTA (Gibco/Invitrogen) and analyzed for densityand viability using haemocytometer (Neubauer). Disassociated cells arewashed and resuspended in their culture media then plated intoPoly-D-Lysine coated Scintiplates (Perkin Elmer) (approximately 100,000cells/well) and incubated at 37° C./5% CO₂ for 20-24 hours. After anextensive wash with Low sodium HEPES-buffered saline solution (LNHBSS)(150 mM Choline Chloride, 20 nM HEPES (Sigma), 1 mM Calcium Chloride, 5mM Potassium Chloride, 1 mM Magnesium Chloride, 10 mM Glucose) the testagents are diluted with LNHBSS and then added to each well at thedesired concentration. (Varying concentrations of test agent may beused). The activation/radiolabel mixture contains an alkaloid such asveratridine or Aconitine (Sigma) or a pyrethroid such as deltamethrin,venom from the scorpion Leiurus quinquestriatus hebraeus (Sigma) and¹⁴C-guanidine hydrochloride (ARC) to measure flux through thevoltage-gated sodium channels.

After loading the cells with test agent and activation/radiolabelmixture, the Poly-D-Lysine coated Scintiplates are incubated at ambienttemperature. Following the incubation, the Poly-D-Lysine coatedScintplates are extensively washed with LNHBSS supplemented withGuanidine (Sigma). The Poly-D-Lysine coated Scintiplates are dried andthen counted using a Wallac MicroBeta TriLux (Perkin-Elmer LifeSciences). The ability of the test agent to block voltage-gated sodiumchannel activity is determined by comparing the amount of ¹⁴C-guanidinepresent inside the cells expressing the different voltage-gated sodiumchannels. Based on this data, a variety of calculations, as set outelsewhere in this specification, may be used to determine whether a testagent is selective for a particular voltage-gated sodium channel.

The IC₅₀ value of a test agent for a specific voltage-gated sodiumchannel may be determined using the above general method. The IC₅₀ maybe determined using a 3, 8, 10, 12 or 16 point curve in duplicate ortriplicate with a starting concentration of 1, 5 or 10 μM dilutedserially with a final concentration reaching the sub-nanomolar,nanomolar and low micromolar ranges. Typically the mid-pointconcentration of test agent is set at 1 μM, and sequentialconcentrations of half dilutions greater or smaller are applied (e.g.0.5 μM; 5 μM and 0.25 μM; 10 μM and 0.125 μM; 20 μM etc.). The IC₅₀curve is calculated using the 4 Parameter Logistic Model or SigmoidalDose-Response Model formula (fit=(A+((B−A)/(1+((C/x)̂D)))).

The fold selectivity, factor of selectivity or multiple of selectivity,is calculated by dividing the IC₅₀ value of the test voltage-gatedsodium channel by the reference voltage-gated sodium channel, forexample, Na_(V)1.5.

Accordingly, the compound of formula (I), the (S)-enantiomer of thecompound of formula (I), i.e., the (S)-enantiomer of the invention, andthe (R)-enantiomer of the compound of formula (I), when tested in thisassay, demonstrated voltage-gated sodium channel blocking activityagainst hNa_(V)1.7 as set forth below in Table 2:

TABLE 2 Compound Chemical Name IC₅₀ (μM) (I)1′-{[5-(trifluoromethyl)furan-2- 0.007yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one(I-R) (R)-1′-{[5-(trifluoromethyl)furan-2- 4.200yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one(I-S) (S)-1′-{[5-(trifluoromethyl)furan-2- 0.003yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one

The concentration-response relationship for the (S)-enantiomer of theinvention and the (R)-enantiomer is shown in FIG. 1. The solid curvesindicate the least-squares best fit to a 1:1 binding isotherm; theIC₅₀'s that describe these curves are given in Table 2. The(S)-enantiomer of the invention demonstrated a significantly higher(i.e. >1000-fold) inhibition potency against hNa_(V)1.7 in this modelwhen compared to the inhibition potency of the corresponding(R)-enantiomer.

These results favor the use of the (S)-enantiomer of the invention overthe (R)-enantiomer or the compound of formula (I) (the racemate) for theutilities described herein in that a higher pharmacological activity maybe achieved at lower dosage levels with possibly fewer side effects.Moreover, the (R)-enantiomer is a very important tool for safety studiesbecause it allows one to distinguish between mechanism-based effects(those mediated by block of sodium channels) and off-target activitiesthat can be eliminated in analogs without compromising efficacy. If anadverse effect is mechanism-based, then the (S)-enantiomer will be muchmore potent then the (R)-enantiomer, as secondary sites of action areunlikely to have identical stereoselectivity and the two enantiomers arelikely to have similar effects, including potency, on secondary sites ofaction.

Biological Example 2 Electrophysiological Assay (In Vitro Assay)

HEK293 Cells expressing hNa_(V)1.7 were cultured in DMEM growth media(Gibco) with 0.5 mg/mL G418, +/−1% PSG, and 10% heat-inactivated fetalbovine serum at 37° C. and 5% CO₂. For electrophysiological recordings,cells were plated on 10 mm dishes.

Whole cell recordings were examined by established methods of whole cellvoltage clamp (Bean et al., op. cit.) using an Axopatch 200B amplifierand Clam pex software (Axon Instruments, Union City, Calif.). Allexperiments were performed at ambient temperature. Electrodes werefire-polished to resistances of 2-4 Mohms Voltage errors and capacitanceartifacts were minimized by series resistance compensation andcapacitance compensation, respectively. Data were acquired at 40 kHz andfiltered at 5 kHz. The external (bath) solution consisted of: NaCl (140mM), KCl (5 mM), CaCl₂ (2 mM), MgCl₂ (1 mM), HEPES (10 mM) at pH 7.4.The internal (pipette) solution consisted of (in mM): NaCl (5), CaCl₂(0.1), MgCl₂ (2), CsCl (10), CsF (120), HEPES (10), EGTA (10), at pH7.2.

To estimate the steady-state affinity of compounds for the resting andinactivated state of the channel (K_(r) and K_(i), respectively), 12.5ms test pulses to depolarizing voltages from −60 to +90 m V from aholding potential of −120 mV was used to construct current-voltagerelationships (I-V curves). A voltage near the peak of the IV-curve (−30to 0 mV) was used as the test pulse throughout the remainder of theexperiment. Steady-state inactivation (availability) curves were thenconstructed by measuring the current activated during a 8.75 ms testpulse following 1 second conditioning pulses to potentials ranging from−120 to −10 mV.

The steady-state voltage-dependence of binding of a compound to avoltage-gated sodium channel was determined by measuring the blockage ofthe ionic current at two holding potentials. Binding to rested-statechannels was determined by using a holding potential of −120 mV, so thatmaximal availability was achieved. Binding to inactivated-state channelswas evaluated at a holding potential such that only about 10% of thechannels were available to open. The membrane potential was held at thisvoltage for at least 10 seconds so that drug binding could equilibrate.

The apparent dissociation constant at each voltage was calculated withthe equation:

${\% \mspace{14mu} {inhibition}} = {\frac{\lbrack{Drug}\rbrack}{\left( {\lbrack{Drug}\rbrack + K_{d}} \right)} \times 100}$

where K_(d) is the dissociation constant (either K_(r) or K_(i)), and[Drug] is the concentration of the test compound.

Accordingly, the compound of formula (I), the (S)-enantiomer of thecompound of formula (I), i.e., the (S)-enantiomer of the invention, andthe (R)-enantiomer of the compound of formula (I), when tested in thismodel, demonstrated affinities for the rested/closed state and theinactivated state of hNa_(V)1.7 as set forth below in Table 3:

TABLE 3 Compound Chemical Name K_(i) (μM) K_(r) (μM) (I)1′-{[5-(trifluoromethyl)furan-2- 0.142 >10 uMyl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one(I-R) (R)-1′-{[5-(trifluoromethyl)furan-2- 0.869 >10 uMyl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one(I-S) (S)-1′-{[5-(trifluoromethyl)furan-2- 0.161 >10 uMyl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′- indol]-2′(1′H)-one

As demonstrated by these results, the (S)-enantiomer of the invention isa state- or voltage-dependent modifier of hNa_(V)1.7, having a lowaffinity for the rested/closed state and a high affinity for theinactivated state. The results demonstrated that the (S)-enantiomer wasabout 5 times more potent in binding to the inactivated-state ofhNa_(V)1.7 than the (R)-enantiomer. Furthermore, the resultsdemonstrated that the (S)-enantiomer is primarily responsible for thepotency of the racemate, i.e., the compound of formula (I).

Biological Example 3 In vivo Assays Acute Pain (Formalin Test)

The formalin test is used as an animal model of acute pain. In theformalin test, animals are briefly habituated to the plexiglass testchamber on the day prior to experimental day for 20 minutes. On the testday, animals are randomly injected with the test articles. At 30 minutesafter drug administration, 50 μL of 10% formalin is injectedsubcutaneously into the plantar surface of the left hind paw of therats. Video data acquisition begins immediately after formalinadministration, for duration of 90 minutes.

The images are captured using the Actimetrix Limelight software whichstores files under the *.llii extension, and then converts it into theMPEG-4 coding. The videos are then analyzed using behaviour analysissoftware “The Observer 5.1”, (Version 5.0, Noldus InformationTechnology, Wageningen, The Netherlands). The video analysis is done bywatching the animal behaviour and scoring each according to type, anddefining the length of the behaviour (Dubuisson and Dennis, 1977).Scored behaviours include: (1) normal behaviour, (2) putting no weighton the paw, (3) raising the paw, (4) licking/biting or scratching thepaw. Elevation, favoring, or excessive licking, biting and scratching ofthe injected paw indicate a pain response. Analgesic response orprotection from compounds is indicated if both paws are resting on thefloor with no obvious favoring, excessive licking, biting or scratchingof the injected paw.

Analysis of the formalin test data is done according to two factors: (1)Percent Maximal Potential Inhibitory Effect (% MPIE) and (2) pain score.The % MPIEs is calculated by a series of steps, where the first is tosum the length of non-normal behaviours (behaviours 1, 2, 3) of eachanimal. A single value for the vehicle group is obtained by averagingall scores within the vehicle treatment group. The following calculationyields the MPIE value for each animal:

MPIE (%)=100−[(treatment sum/average vehicle value)×100%]

The pain score is calculated from a weighted scale as described above.The duration of the behaviour is multiplied by the weight (rating of theseverity of the response), and divided by the total length ofobservation to determine a pain rating for each animal. The calculationis represented by the following formula:

Pain rating=[0(To)+1(T1)+2(T2)+3(T3)]/(To+T1+T2+T3)

CFA Induced Chronic Inflammatory Pain

In this test, tactile allodynia is assessed with calibrated von Freyfilaments. Following a full week of acclimatization to the vivariumfacility, 150 μL of the “Complete Freund's Adjuvant” (CFA) emulsion (CFAsuspended in an oil/saline (1:1) emulsion at a concentration of 0.5mg/mL) was injected subcutaneously into the plantar surface of the lefthind paw of rats under light isoflurane anaesthesia. Animals wereallowed to recover from the anaesthesia and the baseline thermal andmechanical nociceptive thresholds of all animals were assessed one weekafter the administration of CFA. All animals were habituated to theexperimental equipment for 20 minutes on the day prior to the start ofthe experiment. The test and control articles were administrated to theanimals, and the nociceptive thresholds were measured at defined timepoints after drug administration to determine the analgesic responses toeach of the six available treatments. The time points used werepreviously determined to show the highest analgesic effect for each testcompound.

The (S)-enantiomer of the invention and the corresponding (R)-enantiomerwere compared using both oral and topical dosing. FIG. 2 shows acomparison of the efficacy of the (S)-enantiomer of the invention andthe (R)-enantiomer with oral dosing. Each enantiomer was dosed at 10,30, 100 or 200 mg/Kg. The plasma concentration achieved with each dosewas also determined and the reversal of pain response (as the % increasefrom baseline threshold) is plotted as a function of plasmaconcentration.

The (S)-enantiomer had a greater maximal effect when dosed at 200 mg/Kg.The (R)-enantiomer achieved a much higher plasma concentration at anequivalent dose level. This was an unexpected and unusual finding. As aconsequence, the use of the racemate, i.e., the compound of formula (I),would result in about a 10-fold excess of the inactive enantiomer, i.e.,the (R)-enantiomer. Accordingly, the use of the (S)-enantiomer of theinvention would greatly improved the likelihood of obtaining efficacywith minimal chance of encountering off-target activities that are notstereoselective.

The (S)-enantiomer of the invention was also administered topically tothe animals in varying dosages (1%, 2%, 4% and 8% (w/v)) and thenociceptive thresholds measured at defined time points after drugadministration to determine the analgesic responses to each of theavailable treatments. The time points used were previously determined toshow the highest analgesic effect for each test compound.

The response thresholds of the animals to tactile stimuli were measuredusing the Model 2290 Electrovonfrey anesthesiometer (IITC Life Science,Woodland Hills, Calif.) following the Hargreaves test. The animals wereplaced in an elevated Plexiglas enclosure set on a wire mesh surface.After 15 minutes of accommodation, a pre-calibrated Von Frey hair wasapplied perpendicularly to the plantar of the ipsilateral hind paws ofthe animals, with sufficient force, measured in grams, to elicit a crispresponse of the paw. The response indicated a withdrawal from thepainful stimulus and constituted the efficacy endpoint. Testingcontinues until the hair with the lowest force to induce a rapidflicking of the paw was determined or when the cut off force ofapproximately 20 g was reached. This cut off force is used because itrepresent approximately 10% of the animals' body weight and it serves toprevent raising of the entire limb due to the use of stiffer hairs,which would change the nature of the stimulus. The data were expressedas percent increase from baseline threshold measured in grams.

The (S)-enantiomer of the invention, when tested in this model,demonstrated an analgesic effect as set forth below in Table 4.

TABLE 4 % Increase From Base Line (CFB) Compound 1% topical 2% topical4% topical 8% topical (I-S) 0.62 16.71 28.79 45.06

The (S)-enantiomer of the invention at 2%, 4% and 8% (w/v) showedincreases in the von Frey mechanical paw withdrawal thresholds asexpressed by percent increase from baseline (IFB) to indicate ananalgesic effect. The analgesic effect for the (S)-enantiomer increasedwith increasing doses up to the highest dose tested of 8% (w/v), whichshowed the maximum percent IFB at +45.1%. The 1% (w/w) dosage group,however, did not demonstrate an observable increase in von Freymechanical paw withdrawal threshold. The results indicate that the(S)-enantiomer have analgesic effects in the CFA-induced inflammatorypain model in the range of 2% to 8% (w/v).

Postoperative Models of Nociception

In this model, the hypealgesia caused by an intra-planar incision in thepaw is measured by applying increased tactile stimuli to the paw untilthe animal withdraws its paw from the applied stimuli. While animals areanaesthetized under 3.5% isofluorane, which is delivered via a nosecone, a 1 cm longitudinal incision was made using a number 10 scalpelblade in the plantar aspect of the left hind paw through the skin andfascia, starting 0.5 cm from the proximal edge of the heel and extendingtowards the toes. Following the incision, the skin is apposed using 2,3-0 sterilized silk sutures. The injured site is covered with Polysporinand Betadine. Animals are returned to their home cage for overnightrecovery.

The withdrawal thresholds of animals to tactile stimuli for bothoperated (ipsilateral) and unoperated (contralateral) paws can bemeasured using the Model 2290 Electrovonfrey anesthesiometer (IITC LifeScience, Woodland Hills, Calif.). Animals are placed in an elevatedPlexiglas enclosure set on a mire mesh surface. After at least 10minutes of acclimatization, pre-calibrated Von Frey hairs are appliedperpendicularly to the plantar surface of both paws of the animals in anascending order starting from the 10 g hair, with sufficient force tocause slight buckling of the hair against the paw. Testing continueduntil the hair with the lowest force to induce a rapid flicking of thepaw is determined or when the cut off force of approximately 20 g isreached. This cut off force is used because it represent approximately10% of the animals' body weight and it serves to prevent raising of theentire limb due to the use of stiffer hairs, which would change thenature of the stimulus.

Neuropathic Pain Model; Chronic Constriction Injury

In this model, an approximately 3 cm incision was made through the skinand the fascia at the mid thigh level of the animals' left hind legusing a no. 10 scalpel blade. The left sciatic nerve was exposed viablunt dissection through the biceps femoris with care to minimizehaemorrhagia. Four loose ligatures were tied along the sciatic nerveusing 4-0 non-degradable sterilized silk sutures at intervals of 1 to 2mm apart. The tension of the loose ligatures is tight enough to induceslight constriction of the sciatic nerve when viewed under a dissectionmicroscope at a magnification of 4 fold. In the sham-operated animal,the left sciatic nerve was exposed without further manipulation.Antibacterial ointment was applied directly into the wound, and themuscle was closed using sterilized sutures. Betadine was applied ontothe muscle and its surroundings, followed by skin closure with surgicalclips.

The response thresholds of animals to tactile stimuli were measuredusing the Model 2290 Electrovonfrey anesthesiometer (IITC Life Science,Woodland Hills, Calif.). Animals were placed in an elevated Plexiglasenclosure set on a mire mesh surface. After 10 minutes of accommodation,pre-calibrated Von Frey hairs were applied perpendicularly to theplantar surface of both paws of the animals in an ascending orderstarting from the 0.1 g hair, with sufficient force to cause slightbuckling of the hair against the paw. Testing continues until the hairwith the lowest force to induce a rapid flicking of the paw isdetermined or when the cut off force of approximately 20 g is reached.This cut off force is used because it represents approximately 10% ofthe animals' body weight and it serves to prevent raising of the entirelimb due to the use of stiffer hairs, which would change the nature ofthe stimulus.

Thermal nociceptive thresholds of the animals were assessed using theHargreaves test. Following the measurement of tactile thresholds,animals were placed in a Plexiglass enclosure set on top of an elevatedglass platform with heating units. The glass platform wasthermostatically controlled at a temperature of approximately 24 to 26°C. for all test trials. Animals were allowed to accommodate for 10minutes following placement into the enclosure until all explorationbehaviour ceases. The Model 226 Plantar/Tail Stimulator Analgesia Meter(IITC, Woodland Hills, Calif.) was used to apply a radiant heat beamfrom underneath the glass platform to the plantar surface of the hindpaws. During all test trials, the idle intensity and active intensity ofthe heat source were set at 1 and 55 respectively, and a cut off time of20 seconds was used to prevent tissue damage.

The (S)-enantiomer was compared with the corresponding (R)-enantiomerand racemate (compound of formula (I)) in this CCl model using topicalapplication of drug, as described for the CFA model (see FIG. 3). Eachtest compound was administered as an ointment containing 2% (w/v).Consistent with the differing activities of these two enantiomers asvoltage-gated sodium channel inhibitors, only the (S)-enantiomer of theinvention reversed pain responses while the (R)-enantiomer had nosignificant increase from baseline. Both the (S)-enantiomer and theracemate show similar percent increase from baseline which tend tosuggest that the (S)-enantiomer is responsible for the analgesic affect.

Biological Example 4 Aconitine Induced Arrhythmia Assay

The antiarrhythmic activity of compounds of the invention isdemonstrated by the following test. Arrhythmia is provoked byintravenous administration of aconitine (2.0 μg/Kg) dissolved inphysiological saline solution. Test compounds of the invention areintravenously administered 5 minutes after the administration ofaconitine. Evaluation of the anti-arrhythmic activity is conducted bymeasuring the time from the aconitine administration to the occurrenceof extrasystole (ES) and the time from the aconitine administration tothe occurrence of ventricular tachycardia (VT).

In rats under isoflurane anaesthesia (1/4 to 1/3 of 2%), a tracheotomyis performed by first creating an incision in the neck area, thenisolating the trachea and making a 2 mm incision to insert tracheal tube2 cm into the trachea such that the opening of the tube is positionedjust on top of the mouth. The tubing is secured with sutures andattached to a ventilator for the duration of the experiment.

Incisions (2.5 cm) are then made into the femoral areas and using ablunt dissection probe, the femoral vessels are isolated. Both femoralveins are cannulated, one for pentobarbital anaesthetic maintenance(0.02-0.05 mL) and one for the infusion and injection of drug andvehicle. The femoral artery is cannulated with the blood pressure gelcatheter of the transmitter.

The ECG leads are attached to the thoracic muscle in the Lead IIposition (upper right/above heart—white lead and lower left/belowheart—red lead). The leads are secured with sutures.

All surgical areas are covered with gauze moistened with 0.9% saline.Saline (1-1.5 mL of a 0.9% solution) is supplied to moisten the areaspost-surgery. The animals' ECG and ventilation are allowed toequilibrate for at least 30 minutes.

The arrhythmia is induced with a 2 μg/Kg/min aconitine infusion for 5minutes. During this time the ECG is recorded and continuouslymonitored.

Biological Example 5 Ischemia Induced Arrhythmia Assay

Rodent models of ventricular arrhythmias, in both acute cardioversionand prevention paradigms have been employed in testing potentialtherapeutics for both atrial and ventricular arrhythmias in humans.Cardiac ischemia leading to myocardial infarction is a common cause ofmorbidity and mortality. The ability of a compound to preventischemia-induced ventricular tachycardia and fibrillation is an acceptedmodel for determining the efficacy of a compound in a clinical settingfor both atrial and ventricular tachycardia and fibrillation.

Anaesthesia is first induced by pentobarbital (i.p.), and maintained byan i.v. bolus infusion. Male SD rats have their trachea cannulated forartificial ventilation with room air at a stroke volume of 10 mUKg, 60strokes/minute. The right femoral artery and vein are cannulated withPE50 tubing for mean arterial blood pressure (MAP) recording andintravenous administration of compounds, respectively.

The chest is opened between the 4^(th) and 5^(th) ribs to create a 1.5cm opening such that the heart was visible. Each rat is placed on anotched platform and metal restraints are hooked onto the rib cageopening the chest cavity. A suture needle is used to penetrate theventricle just under the lifted atrium and exited the ventricle in adownward diagonal direction so that a >30% to <50% occlusion zone (OZ)would be obtained. The exit position is ˜0.5 cm below where the aortaconnects to the left ventricle. The suture is tightened such that aloose loop (occluder) is formed around a branch of the artery. The chestis then closed with the end of the occluder accessible outside of thechest.

Electrodes are placed in the Lead II position (right atrium to apex) forECG measurement as follows: one electrode is inserted into the rightforepaw and the other electrode is inserted into the left hind paw.

The body temperature, mean arterial pressure (MAP), ECG, and heart rateare constantly recorded throughout the experiment. Once the criticalparameters have stabilized, a 1-2 minute recording is taken to establishthe baseline values. Infusion of a compound of the invention or controlsubstance is initiated once baseline values are established. After a5-minute infusion of compound or control, the suture is pulled tight toligate the LCA and create ischemia in the left ventricle. The criticalparameters are recorded continuously for 20 minutes after ligation,unless the MAP reaches the critical level of 20-30 mm Hg for at least 3minutes, in which case the recording is stopped because the animal wouldbe declared deceased and is then sacrificed. The ability of compounds ofthe invention to prevent arrhythmias and sustain near-normal MAP and HRis scored and compared to control.

Biological Example 6

Compared to the racemate, i.e., the compound of formula (I), the(S)-enantiomer, substantially free of the (R)-enantiomer, has a bettersolubility profile in a variety of pharmaceutically acceptableexcipients. Thus, the (S)-enantiomer can be formulated in a fewer numberof dosage units than the racemate. This property facilitates dosingpatients at a higher level if needed to achieve efficacy. Examples ofthe difference in solubility are shown in Table 5 below:

TABLE 5 Compound of formula (I) Excipient (racemate) (S)-enantiomerLabrasol ® 72.5 mg/mL 231 mg/mL Propylene glycol 2.7 mg/mL 9.8 mg/mL PEG400 <50 mg/mL >55 mg/mL Capryol ® 90 18.1 mg/mL 96 mg/mL Tween ® 80 64mg/mL >123 mg/mL Ethanol 10.0 mg/mL 36.4 mg/mL Labrasol ®/PEG 400 60/4070.4 mg/mL 182 mg/mL Labrasol ®/Capryol ® 90 60/40 44.4 mg/mL 191 mg/mLLabrasol ®/Transcutol ® 60/40 74.2 mg/mL 186 mg/mL

Biological Example 7 In Vivo Assay for Treatment of Pruritis

Histamine induces pruritis (itching) in humans. Accordingly, this assayevaluates the efficacy of topically and orally administered(S)-enantiomer of the invention on histamine-induced pruritis in maleICR mice.

The animals were randomly divided into test groups including anuntreated group, a group treated with a topical pharmaceuticalcomposition with 8% (w/v) (S)-enantiomer, and a group treated with anoral pharmaceutical composition of 50 mg/Kg (S)-enantiomer. One dayprior to testing, the scapular regions on the animals were shaved withhair clippers. On the testing day, the animals were habituated for 60minutes in the test chamber comprising of a clear plastic tube placedvertically on a flat surface. After the habituation period, the animalswere removed from the plastic tube, placed in a restrainer, and injectedwith histamine at the shaved scapular region. The injections were madeintradermally into the skin in small injection volumes (10 μL) using aHamilton syringe. The injection solutions consisted of histaminedissolved in saline at a concentration of 100 μg/10 μL (or 10 mg/mL). 10μg of the solution was injected into each mouse. Immediately after theinjections, the animals were returned to the test chambers and observedby cameras placed above the test chambers for a total of 50 minutes. Thecameras were connected to a computer where digital video files werecreated, saved, and analyzed.

The number of itching bouts was scored over 40 minutes. An “itchingbout” was defined as the lifting of a hind leg, using it to scratch thescapular region, and then placing it back on the ground. Alternatively,if instead of placing the hind leg back on the ground the mouse wasobserved to lick the paw, then that too was counted as an itching bout.

To the untreated group, animals (n=7) were habituated in the testchamber for 60 minutes prior to the histamine injection. To evaluatetopical (S)-enantiomer in the histamine-induced pruritis, animals(n=16/group) were habituated in the test chamber for 30 minutes,followed by the application of 50 mg of 8% (w/v) topical (S)-enantiomeror vehicle to the shaved region on the back. The animals were returnedto the test chamber for another 30 minutes of habituation prior to theinjection of histamine. To evaluate oral (S)-enantiomer, animals(n=8/group) were dosed by oral gavage with 50 mg/Kg (S)-enantiomer orvehicle followed by habituation in the test chamber for 60 minutes priorto the histamine injection.

The data were analyzed using GraphPad Prism 5 statistical analysissoftware and an unpaired t-test was used for univariate analysis.Results are expressed as mean±SEM. Values that reached a p<0.05 level ofsignificance were considered statistically significant.

Results

The injection of histamine into the skin caused the animals to itchsporadically in bouts that lasted 1-2 seconds. In the untreated group,itching bouts began immediately post-injection and lasted for roughly 40minutes thereafter (see FIG. 4). The group treated with 8% (w/v) oftopical (S)-enantiomer showed significantly reduced pruritis (see FIG.5). Animals treated with the vehicle only had a total number of134.3±13.31 (n=16) itching bouts whereas mice treated with topical(S)-enantiomer had 89.00±10.51 (n=16) itching bouts. The differencebetween these groups was statistically significant with a p value of0.0122. The group treated with 50 mg/Kg oral (S)-enantiomer similarlyshowed significantly reduced pruritis (see FIG. 6). Animals treated withvehicle only had a total number of 42.88±6.667 (n=8) itching boutswhereas mice treated with (S)-enantiomer had 17.25±6.310 (n=8) itchingbouts. The difference between the orally-treated groups was alsostatistically significant with a p value of 0.0144. The resultsdemonstrated that orally and topically administered (S)-enantiomerreduced pruritis. Furthermore, it is apparent that two common modes ofdrug delivery, oral and topical, can be used to deliver the(S)-enantiomer to achieve this therapeutic effect.

Biological Example 8 Clinical Trial in Humans for the Treatment ofPrimary/Inherited Erythromelalgia (IEM)

Primary/Inherited Erythromelalgia (IEM) is a rare inherited paincondition. The underlying cause of IEM can be one or moregain-of-function mutation(s) in the Na_(V)1.7 voltage-gated sodiumchannel, which the (S)-enantiomer of the invention has been shown toinhibit.

Human patients with IEM have recurrent episodes of intense burning painassociated with redness and warmth in the hands and feet, but eventuallythe pain becomes constant. The pain is relieved by cooling, but has beenlargely resistant to pharmacological intervention. However, there arereports of voltage-gated sodium channel blockers showing moderate tooutstanding pain relief for this condition.

A clinical trial for determining the efficacy of the (S)-enantiomer ofthe invention in ameliorating or alleviating IEM can be designed to be athree-period, double-blind, multiple-dose, and crossover study tominimize the dropout rate of participants, and will take intoconsideration that the patients enrolled will only be available for a10-day study. Each patient enrolled in the study will serve as their owncontrol, receiving both placebo and 400 mg of the (S)-enantiomer of theinvention twice daily in a cross-over fashion.

Biological Example 9 Clinical Trial in Humans for Treatment of DentalPain

The purpose of this clinical trial was to compare the safety andefficacy (onset, duration of relief, and overall efficacy) of a single500 mg dose of the (S)-enantiomer of the invention versus placebo dosefor relief of pain following extraction of impacted third molar teeth.

Sixty-one subjects were enrolled in the study. The mean age for thesubjects was 20.4 years, and all subjects were male. The majority ofsubjects were Caucasians (95.1%).

The severity and relief of the pain was measured using an 11-point PainIntensity Numerical Rating Scale (graded from 0=no pain at all to10=worst pain imaginable) (PINRS) and a 5-point Categorical Pain ReliefScale (REL). Subjects completed the PINRS after surgery, but before theadministration of (S)-enantiomer of the invention. Efficacy variableswere derived from the REL and PINRS scores and included total painrelief (TOTPAR), pain intensity difference (PID), and summed painintensity difference (SPID) and evaluated at time points of 4, 6, 8, and12 hours after administration of the (S)-enantiomer of the invention.

However, the primary and all secondary endpoints showed a consistentanalgesic trend with distinct separation of the (S)-enantiomer fromplacebo. These results suggest that the (S)-enantiomer has analgesicproperties, but statistical significance from the placebo was notachieved due to two main reasons: (1) relatively high placebo responserate and (2) the slow onset of action of the (S)-enantiomer. The dentalmodel utilized is designed and best suited for the evaluation of drugswith rapid onset such as the NSAID class of antiinflammatory agents. Itwas evident from this study that the (S)-enantiomer of the invention didnot have such a NSAID-like rapid onset of action. However, the painrelief demonstrated by those subjects who received the (S)-enantiomerwas higher compared to those subjects who only received the placebo,sufficiently so that the total efficacy population showed a consistentanalgesic signal for all endpoints evaluated.

Biological Example 10 Clinical Trial in Humans for the Safety of the(S)-enantiomer of the Invention

This clinical trial was a Phase 1, randomised, double-blind,placebo-controlled study in healthy subjects to evaluate the safety andpharmacokinetics of topically applied ointment containing the(S)-enantiomer of the invention.

The (S)-enantiomer ointment was applied daily for 21 consecutive days todetermine the local skin toxicity/irritancy of the (S)-enantiomer.Systemic pharmacokinetics and local skin drug levels were also assessed.The systemic exposure to the (S)-enantiomer following topicalapplications and local skin irritation following multiple-doses of the(S)-enantiomer ointment were evaluated. Each subject received 5treatments for 21 consecutive days: (S)-enantiomer as ointment with 4%and 8% (w/w) (1×100 μL; Treatments A and B, respectively), placebo asointment (Treatment C), saline (0.9%) solution (1×100 μL; negativecontrol; Treatment D), and sodium-lauryl-sulphate (SLS) 0.1% solution(1×100 μL; positive control; Treatment E). The treatments were appliedon two different sites on each subject's upper back in an occludedmanner (five treatments) and partially occluded manner (first threetreatments). The location for each treatment on each site (Treatments A,B, C, D, and E on occluded site and Treatments A, B, and C on partiallyoccluded site) was randomised. Subjects were confined to the clinicalresearch facility from approximately 18 hours prior to the first dosingon Day 1 until approximately 8 hours post-2^(nd) dose (Day 2). Subjectscame back each day for 19 consecutive days (Days 3 to 21) for dosing andstudy procedures.

No Serious Adverse Events (SAEs) or deaths were reported. All AdverseEvents (AEs) were mild or moderate in severity, with the majority of AEsrelated to local skin reactions from the surgical tape used to adherethe occlusive dressings. All subjects reacted to the positive control.The positive control was stopped in all subjects on Day 4 followingcomplaints of excessive discomfort from the subjects. Skin irritationscores were low for all treatments administered (maximum score of 3measured on a scale of 0-7) indicating that (S)-enantiomer ointment waslocally well tolerated. No difference was observed between cumulativeirritation scores for (S)-enantiomer 4% (w/w), (S)-enantiomer 8% (w/w),placebo ointments and the negative control (0.9% saline). Signs ofirritation had completely resolved by Day 28 (7 days following the finaldose) for the majority of subjects.

Electrocardiography tracings did not demonstrate clinically significantchanges in pulse rate, quiescent resting state, or QT_(c) intervals ofthe subjects and no clinically significant changes from baseline wereobserved in the subjects' vital signs, physical examinations, orlaboratory assessments. Systemic exposure to (S)-enantiomer wasnegligible, as (S)-enantiomer concentrations in plasma were below thelower limit of quantification (LLOQ) (0.1 ng/mL or 100 pg/mL) in mostsamples (489 out of 546−˜90%). The highest level of (S)-enantiomerobserved in one subject during the dosing period (Day 22) was 994 pg/mL.Based on the minimal local irritation and favourable safety profile,together with low (S)-enantiomer systemic exposure, it was concludedthat the (S)-enantiomer of the invention was well tolerated and safe asa topical analgesic.

Biological Example 11 Clinical Trial in Humans for Treatment ofPost-Herpetic Neuralgia

Post Herpetic Neuralgia (PHN) is a well established and well recognizedmodel for studying neuropathic pain. Furthermore, PHN demonstratesstrong evidence of sodium channel blocker efficacy. The following studyrepresents a randomized, double-blind, placebo-controlled,two-treatment, two-period cross-over study to evaluate the safety,tolerability, preliminary efficacy and systemic exposure of the(S)-enantiomer of the invention topically administered to patients withPHN. The primary objectives are (a) to compare the safety and efficacyof an ointment containing the (S)-enantiomer to that of placebo for therelief of pain in patients with PHN, and (b) to evaluate the extent ofsystemic exposure of the (S)-enantiomer following topical application of(S)-enantiomer in patients with PHN. The treatments will consist of(S)-enantiomer 8% (w/w) ointment and the matching placebo ointment.

The study will include the following four periods:

1. An initial screening and washout period (up to 3 weeks);

2. A single-blind, placebo run-in period (1 week);

3. A cross-over treatment period that will consist of 2 treatmentperiods each lasting 3 weeks separated by 2 weeks ofwashout/single-blind placebo run-in (total of 8 weeks); and

4. A safety follow-up period (2 weeks).

All of the U.S. patents, U.S. patent application publications, U.S.patent applications, foreign patents, foreign patent applications andnon-patent publications referred to in this specification areincorporated herein by reference in their entireties.

Although the foregoing invention has been described in some detail tofacilitate understanding, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claims.Accordingly, the described embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalents of the appended claims.

1.-7. (canceled)
 8. A method of treating a disease or a condition in amammal selected from pain, pruritis, multiple sclerosis, depression,cardiovascular diseases, respiratory diseases, psychiatric diseases,neurological diseases and seizures, and combinations thereof, whereinthe method comprises administering to the mammal in need thereof atherapeutically effective amount of the (S)-enantiomer of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onehaving the following formula (I-S):

or a pharmaceutically acceptable solvate or prodrug thereof.
 9. Themethod of claim 8 wherein the disease or condition is pain.
 10. Themethod of claim 9, wherein the pain is selected from neuropathic pain,inflammatory pain, visceral pain, cancer pain, dental pain, chemotherapypain, trauma pain, surgical pain, labor pain, neurogenic bladder,ulcerative colitis, chronic pain, persistent pain, peripherally mediatedpain, centrally mediated pain, chronic headache, migraine headache,sinus headache, tension headache, phantom limb pain and peripheral nerveinjury, and combinations thereof.
 11. The method of claim 9, wherein thepain is associated with a disease or condition selected from HIV, HIVtreatment induced neuropathy, heat sensitivity, sarcoidosis, irritablebowel syndrome, Crohns disease, multiple sclerosis, amyotrophic lateralsclerosis, pruritis, hypercholesterolemia, benign prostatic hyperplasia,diabetic neuropathy, peripheral neuropathy, rheumatoid arthritis,osteoarthritis, paroxysmal dystonia, myasthenia syndromes, myotonia,malignant hyperthermia, cystic fibrosis, pseudoaldosteronism,rhabdomyolysis, bipolar depression, anxiety, schizophrenia, sodiumchannel toxin related illnesses, Paroxysmal Episodic Pain Disorder,cancer, epilepsy, partial and general tonic seizures, restless legsyndrome, arrhythmias, ischaemic conditions caused by stroke or neuraltrauma, tachy-arrhythmias, atrial fibrillation and ventricularfibrillation.
 12. The method of claim 9 wherein the pain is selectedfrom trigeminal neuralgia, post-herpetic neuralgia, eudynia, familialerythromelalgia, primary erythromelalgia, familial rectal pain orfibromyalgia.
 13. The method of claim 8 wherein the disease or conditionis pruritis.
 14. The method of claim 8 wherein the disease or conditionis multiple sclerosis.
 15. A method of treating a disease or conditionin a mammal by the inhibition of ion flux through a voltage-gated sodiumchannel in the mammal, wherein the method comprises administering to themammal in need thereof a therapeutically effective amount of the(S)-enantiomer of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onehaving the following formula (I-S):

or a pharmaceutically acceptable solvate or prodrug thereof.
 16. Amethod of decreasing ion flux through a voltage-gated sodium channel ina cell in a mammal, wherein the method comprises contacting the cellwith the (S)-enantiomer of1-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onehaving the following formula (I-S):

or a pharmaceutically acceptable solvate or prodrug thereof.
 17. Amethod for preparing the (S)-enantiomer of1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onehaving the following formula (I-S):

wherein the method comprises: (a) treating a compound of the followingformula:

with 2-bromomethyl-5-trifluoromethylfuran under suitable conditions toform a compound of formula (I):

(b) isolating the (S)-enantiomer1′-{[5-(trifluoromethyl)furan-2-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-onefrom the compound of formula (I) by suitable chiral high pressure liquidchromatography conditions or by suitable simulated moving bedchromatography conditions.